'We must annihilate Islamic State worldwide' - world leaders vow to hunt down terrorist leaders
Western leaders have stepped up the rhetoric against Islamic State (IS) as residents of the Belgian capital Brussels awoke to largely empty streets, with the city entering its second day under the highest terrorism threat level.
Brussels kept its subways and underground trams closed for a second day amid the menace of potential Paris-style attacks.
Officials have also recommended that sports competitions and all activities in public buildings in the Belgian capital should be cancelled, with malls and shopping centres closed.
Adding to the threat is the knowledge that a missing suspect in the November 13 massacres in the French capital was last spotted crossing into Belgium.
Western leaders have vowed to stand up to IS, which has claimed responsibility for the attacks in Paris that killed 130 people and wounded hundreds more, the suicide bombings in Beirut that killed 43 people and injured more than 200, and the downing of the Russian airline carrying 224 people in Sinai. All these incidents took place within the past month.
Speaking from Kuala Lumpur, US president Barack Obama said the world would not accept the extremists' attacks on civilians as the "new normal," and vowed the US and its international partners would not relent in the fight against the Islamic militants.
French defence minister Jean-Yves Le Drian said IS must be destroyed at all costs.
"We must annihilate Islamic State worldwide ... and we must destroy Islamic State on its own territory," Mr Le Drian said.
"That's the only possible direction."
France has intensified its aerial bombardment in Syria. Mr Le Drian added that French aircraft carrier Charles de Gaulle, which has been sent to help operations against IS militants in Syria, will be "operational" from Monday and "ready to act".
French president Francois Hollande is scheduled to meet in Paris with UK Prime Minister David Cameron on Monday, and will travel to Washington and Moscow later in the week to push for a stronger international coalition against IS.
Mr Cameron is expected to outline his plan for combating the Islamic militants this week as he seeks Parliamentary approval to join France, the US and Russia in striking the group's strongholds in Syria.
Tensions have been high in Europe since the attacks in Paris.
France has extended a state of emergency - which allows police raids, searches and house arrest without permission from a judge - for three months. On Saturday, a ban on demonstrations and other gatherings was extended through until November 30, when a UN climate conference featuring more than 100 heads of state is scheduled to start.
All the usual markets in Brussels were cancelled on Sunday and the Belgian minister of education, Joelle Milquet, told Le Soir newspaper that there was a "50% chance" schools would be closed on Monday.
Bernard Clerfayt, mayor of the Brussels suburb of Schaerbeek, told Belgian media that the capital is still under a grave threat. He said that as long as this threat is present, it is essential to remain very vigilant.
Several of the Paris attackers had lived in Brussels, including suspected mastermind Abdelhamid Abaaoud, who was killed in a stand-off with French police on Wednesday.
Salah Abdeslam, another suspected attacker, is at large and is known to have crossed into Belgium the morning after the attacks.
In the Turkish coastal city of Antalya, authorities have detained a 26-year-old Belgian citizen, suspected of being connected to Islamic extremists and possibly to the Paris attacks - raising hopes of a possible breakthrough in the investigation.