Watch: A timeline of terror attacks in Europe since 2015
Many European countries have seen deadly terror incidents in the recent years.
A bomb attack in Manchester Arena that killed 22 people, including children, and injured 59 has been described as the the worst terrorist incident to hit Britain since the July 7 atrocities.
A 23-year-old man has been arrested in connection with the explosion that took place in the foyer of as thousands of people were leaving a concert by Ariana Grande.
As counter-terrorism agencies begin a major operation to establish the circumstances of the attack and the bomber’s background, we look back at the terror atrocities across Europe in recent years:
January 7, 2015: Charlie Hebdo attack
Death toll: 12
Bloodshed was brought to Paris by gunmen who launched three days of attacks in the capital and surrounding regions. The massacre started with an attack at the offices of satirical magazine Charlie Hebdo, killing 12 people.
It ended with a huge police operation and two sieges. During the bloodshed, another militant killed a policewoman and took hostages at a supermarket killing four before police shot him dead.
November 13, 2015: Paris attacks
Death toll: 130
Suicide bomb-and-gun attacks killed 130 people across Paris, including 89 at the Bataclan music venue. More than 360 people were wounded. IS claimed responsibility.
March 22, 2016: Brussels bombings
Death toll: 32
Three IS bombers killed 32 people at Brussels airport and on the capital’s subway. The blasts took place during the morning rush-hour. The bombers were all Belgian.
July 14, 2016: Nice lorry attack
Death toll: 84
A truck ploughed into Bastille Day revellers in the southern French city of Nice, killing 86 people. IS claimed responsibility for the attack, which was carried out by a Tunisian living in France.
July 22, 2016: Munich shooting
Death toll: 9
An 18-year-old German-Iranian gunman, who was not known to police, opened fire at a crowded shopping centre and fast-food restaurant in Munich, killing nine people and injuring 36, including children.
July 26, 2016: Normandy church
Death toll: 1
Two attackers killed 85-year-old parish priest Father Jacques Hamel with a blade and seriously wounded another hostage in a church in northern France before being shot dead by French police.
The two hostage-takers had pledged allegiance to Islamic State. The men arrived as Fr Hamel was leading morning Mass in Saint-Etienne-du-Rouvray, a working-class town near Rouen, north-west of Paris.
December 19, 2016: Berlin truck
Death toll: 12
A truck ploughed into a crowded Christmas market in central Berlin, killing 12 people and injuring 56 others.
February 3, 2017: Louvre knife attack
Death toll: 0
A machete-wielding man shouting “Allahu akbar” attacked French soldiers guarding the sprawling building at the Louvre museum.
The suspect, who was shot four times, was later named by officials as Egyptian Abdullah Reda Refaie al-Hamahmy, 28.
March 22, 2017: Westminster attack
Death toll: 5
Khalid Masood drove a hired car over Westminster Bridge, near the Houses of Parliament, mounted the pavement and hit pedestrians before crashing into railings outside the Palace of Westminster.
He stabbed Pc Keith Palmer to death and also killed US tourist Kurt Cochran, Romanian tourist Andreea Cristea, 31, plus Britons Aysha Frade, 44, and 75-year-old Leslie Rhodes. Masood was shot dead by police.
April 7, 2017: Stockholm truck
Death toll: 4
A stolen truck was rammed into a crowd in the Swedish capital, killing four people and wounding 15 others. A 39-year-old Uzbek man is believed to have confessed to the crime. Police said Rakhmat Akilov was known to have been sympathetic to extremist organisations.
Briton Chris Bevington, 41, who lived in Stockholm with his family and worked as a director with music streaming service Spotify, was among the victims.
April 20, 2017: Paris shooting
Death toll: 1
A gunman opened fire on a police car parked at Champs-Elysees in Paris and killed an officer before he was shot dead.
French officials said the suspect in the attack was previously flagged as an extremist. He was also convicted in 2003 of attempted murder in the shooting of two police officers. Islamic State claimed responsibility for the attack.