ISLAMIC extremists struck in the heart of Europe on Tuesday, killing at least 31 people and wounding scores of others in back-to-back bombings of the Brussels airport and subway.
Bloodied and dazed travellers staggered from the airport after two explosions - at least one blamed on a suicide attacker and another reportedly on a suitcase bomb - tore through crowds checking in for morning flights.
About 40 minutes later, another blast struck subway commuters in central Brussels near the Maelbeek station, which sits amid the European Commission headquarters.
Authorities released a photo taken from closed-circuit TV footage of three men pushing luggage trolleys, saying two of them apparently were the suicide bombers and that the third - dressed in a light-coloured coat, black hat and glasses - was at large. They urged the public to contact them if they recognised him. The two men believed to be the suicide attackers apparently were wearing dark gloves on their left hands.
Belgian newspaper La Libre said that its sources said the gloves may have been worn to hide detonator devices.
In police raids across Brussels, authorities later found a nail-filled bomb, chemical products and an Islamic State flag in a house in the Schaerbeek neighbourhood, the state prosecutors' office said in a statement.
In its claim of responsibility, the Islamic State group said its members detonated suicide vests both at the airport and in the subway, where many passengers fled to safety down dark tunnels filled with hazy smoke from the explosion in a train pulling away from the platform.
As the city went into lockdown:
* Local media reported that 20 people were killed following the blast at Maelbeek metro station, while 14 died in the suicide attack at the airport. Other agencies said 31 in total have been confirmed dead.
* The number of people injured in both attacks was believed to be 198
* Two Kalashnikov rifles and an unexploded bomb belt were found at the airport
* No Irish people are believed to have been injured in the attacks
European security officials have been braced for a major attack and warned that IS was actively preparing to strike. The arrest on Friday of Salah Abdeslam, a key suspect in the Paris attacks last November, heightened those fears, as investigators said many more people were involved than originally thought and that some are still on the loose.
"In this time of tragedy, this black moment for our country, I appeal to everyone to remain calm but also to show solidarity," said Belgian Prime Minister Charles Michel, who announced three days of mourning in his country's deadliest terror strike.
"Last year it was Paris. Today it is Brussels. It's the same attacks," said French President Francois Hollande.
In Brussels Airport. Been evacuated afer suspected bomb.— Luke Mac an Bháird (@Luke_Mac_) March 22, 2016
Advice to people. Don't come to Gate B at Brussels Airport. We have been evacuated to back of the terminal. Ppl crying and very scared.— Luke Mac an Bháird (@Luke_Mac_) March 22, 2016
So my gate and another one has been told to stay put inside the airport...this is crazy stuff.— Luke Mac an Bháird (@Luke_Mac_) March 22, 2016
Being evacuated to the tarmac now. pic.twitter.com/lu1k3kmsEZ— Luke Mac an Bháird (@Luke_Mac_) March 22, 2016
Stampede now. Everyone running— Luke Mac an Bháird (@Luke_Mac_) March 22, 2016
There was a moment of intense worry as people shouted 'run'. On the tarmac now though. pic.twitter.com/n1O63vJgTR— Luke Mac an Bháird (@Luke_Mac_) March 22, 2016
Belgium raised its terror alert to the highest level, shut the airport and ordered a city-wide lockdown, deploying about 500 soldiers onto Brussels' largely empty streets to bolster police checkpoints. France and Belgium both reinforced border security.
Medical officials treating the wounded said some victims lost limbs, while others suffered burns or deep gashes from shattered glass or suspected nails packed in with explosives. Among the most seriously wounded were several children.
The bombings came barely four months after suicide attackers based in Brussels' Molenbeek district slaughtered 130 people at Paris nightspots, and intelligence agencies had warned for months a follow-up strike was inevitable. Those fears increased following Abdeslam's arrest in Molenbeek, along with police admissions that others suspected of links to the Paris attacks were at large.
A high-level Belgian judicial official said a connection by Abdeslam to Tuesday's attacks is "a lead to pursue".
Abdeslam has told investigators he was planning to "restart something" from Brussels, said Belgian Foreign Minister Didier Reynders. He said on Sunday that authorities took the claim seriously because "we found a lot of weapons, heavy weapons in the first investigations and we have seen a new network of people around him in Brussels".
There have been 2 explosions at the airport. Building is being evacuated. Don't come to the airport area.— Brussels Airport (@BrusselsAirport) March 22, 2016
Don't come to the airport - airport is being evacuated. Avoid the airport area. Flights have been cancelled.— Brussels Airport (@BrusselsAirport) March 22, 2016
Explosions and smoke at Brussels Airport. Evacuation underway. pic.twitter.com/Ufn1TwQri4— Declan Varley (@declanvarley) March 22, 2016
I'm in terminal A departure hall at @BrusselsAirport and no one seems to know what is going on. No security staff to be found anywhere.— C McDonald-Gibson (@cmcdonaldgibson) March 22, 2016
My uncle works at Brussels Airport. Just called that he's okay, but that everyone is in full panic. Windows are all broken.— Jill (@autumnalsoul) March 22, 2016
IMAGE: Damage inside Brussels airport pic.twitter.com/Y5hNpM8RhG— The Int'l Spectator (@intlspectator) March 22, 2016
While they knew that some kind of extremist act was being prepared in Europe, they were surprised by the size of Tuesday's attacks, said Belgian Interior Minister Jan Jambon.
"It was always possible that more attacks could happen, but we never could have imagined something of this scale," he said.
Officials at the airport in the Brussels suburb of Zaventem said police had discovered a Kalashnikov assault rifle and an explosives-packed vest abandoned at the facility, offering one potential lead for forensic evidence. Bomb disposal experts safely dismantled that explosive device.
A US administration official said American intelligence officers were working with European counterparts to try to identify the apparently skilled bomb-makers involved in the Brussels attacks and to identify any links to bombs used in Paris.
The official said that at least one of the bombs at the airport was suspected to have been packed in a suitcase left in the departures hall.
Three intelligence officials in Iraq told the AP that they had warned European colleagues last month of IS plans to attack airports and trains, although Belgium was not specified as a likely target.
One of the officials said Iraqi intelligence officials believe that three other IS activists remain at large in Brussels and are plotting other suicide-bomb attacks.
Leaders of the European Union said in a joint statement that Tuesday's assault on Brussels "only strengthens our resolve to defend European values and tolerance from the attacks of the intolerant".
Reflecting the trauma of the moment, Belgian officials offered uncertain casualty totals at both the airport and subway, where police conducted controlled explosions on suspicious abandoned packages that ultimately were found to contain no explosives.
Belgium's health minister, Maggie de Block, said 11 people were killed and 81 injured at the airport, where thousands of passengers were waiting to check luggage and collect boarding cards.
Brussels Mayor Yvan Mayeur said 20 people died and more than 100 were wounded in the subway blast. Rescue workers set up makeshift first aid centres in a nearby pub and hotel.
Passengers on other trains said many commuters were reading about the airport attacks on their smartphones when they heard the subway blast. Hundreds fled from stopped trains down tunnel tracks to adjacent stations.
Political leaders and others around the world expressed their shock at the attacks.
"We will do whatever is necessary to support our friend and ally Belgium in bringing to justice those who are responsible," US President Barack Obama said.
Belgium's king and queen said they were "devastated" by the violence, describing the attacks as "odious and cowardly".
After nightfall, Europe's best-known monuments - the Eiffel Tower, the Brandenburg Gate and the Trevi Fountain - were illuminated with Belgium's national colours in a show of solidarity.
An Irish student on Erasmus in Brussels has documented the evacuation from the airport.
Law and politics student Luke Mac an Bháird said the crowd at Gate B at Brussels Airport were evacuated to the back of the terminal.
The crowd were first told to remain put, before they were evacuated to a tarmac area at the back of the terminal.
He described how a stampede began as panic set in.
"There was a moment of intense worry as people shouted 'run'. On the tarmac now though," he tweeted.
"There was just a mass of people at once running to the bottom of the gates, they were saying that another bomb was coming," he told the Anton Savage Show on TodayFM.
"I didn't know what was going on. It was very confusing."
"Ever since what happened in Paris last year, there's always an army presence [in Brussells]. Even this morning when I got the train to go to the airport the army was there but there was nothing different today though to suggest that something was [about to happen].
"What really put it into perspective for me was hearing thousands of people shouting all at once," he said.
Irish man Ian McCafferty, who was underground at the next Metro station said the crowd heard a 'muffled thud' and panic set in.
"There was a loud muffled thud, it was very audible. There was a lot of dust and smoke raised at the metro station," he told Sky News.
"Soldiers who are always on hand these days were very quick to evacuate the building.
"There was a lot of people crying.
"The initial shock of the explosion would have lifted a lot of dust through the tunnels and once we were evacuated from the building we saw some smoke.
The Minister for Foreign Affairs and Trade, Charlie Flanagan TD has expressed his shock at this morning's explosions in Brussels.
"I am horrified by reports of multiple explosions in Brussels, Belgium and my thoughts are with those affected.
"The Consular Section of my Department, in conjunction with our Embassy in Belgium, are working with the local authorities.
"Anyone with concerns for family and friends can contact the Consular Division of my Department on +353 1 418 0200.
"Any Irish citizens in Brussels or Belgium should exercise caution and closely follow the instructions of local authorities.
"We will be updating our guidance in consultation with the Authorities as this situation unfolds."
A Sky News journalist at the scene reported security at the airport to be requesting people to leave their hand luggage and head out of the building immediately.
Sky News television’s Alex Rossi was at the scene and said he heard two very loud explosions.
“I could feel the building move. There was also dust and smoke as well … I went towards where the explosion came from and there were people coming out looking very dazed and shocked,” he said.
The European Confederation of Police has released a statement this morning saying that the latest incident reminds us "once again of the dangers and threats facing our citizens."
EuroCOP extends their sympathies to those who have been impacted, people who have lost loved ones or have been injured themselves.
"At this time it appears police officers in Brussels are dealing with a coordinated terrorists attack. These attacks have left several dead and many more injured," EuroCOP's Àngels Bosch said.
“Once again incidents such as this serve to remind us of bravery shown by police officers as they place themselves in harms way so others don't have to.
“All Europeans can be grateful that they are served by such courageous men and women giving their all in attempts to keep them safe.
“I want to be very clear however that brave men and women is not enough. We must ensure our police forces cooperate in a way they never have before. Recent events have shown us that terrorism knows no borders."
Flags are currently being put at half mast outside the European Commission.
A minute of silence has been held outside the Spanish parliament and Madrid's town hall at noon in memory of the victims.
Today's attacks show "the most brutal and inhumane side of those who know only the language of violence and terror", said a spokesperson for the Spanish government.
President Barack Obama has sent a message of support to the people of Brussels, saying: "We can and we will defeat those who threaten the safety and security of people all around the world."
The Eiffel Tower will show the colours of the Belgium flag tonight in an act of solidarity following this morning's attacks.