Belgian capital Brussels has entered its third day of lockdown, with schools and underground transport shut and more than 1,000 security personnel deployed across the country.

Belgian interior minister Jan Jambon said “investigations will continue until we’ve fixed this problem”.

He told Belgium’s RTL broadcaster that Paris attacks fugitive Salah Abdeslam “must have a lot of support on our territory. That’s why all these searches being conducted at the moment are important”.

Security was extra tight in the European quarter of Brussels, especially around the EU institutions where ministerial meetings were going ahead as planned.

Brussels remains at maximum alert over information about an “imminent threat”, possibly a series of co-ordinated attacks at different locations similar to those in Paris on November 13.

Belgian police carried out raids throughout Brussels on Sunday, detaining 16 people, but Abdeslam was not among those arrested

Federal prosecutor Eric Van Der Sypt said 19 raids were carried out in Molenbeek, home to many of the Paris attackers, and other boroughs of Brussels and three raids were carried out in other cities.

“We have to stress that no firearms or explosives were discovered … during the raids,” Mr Van Der Sypt said.

One of those detained was injured when a car he was in tried to ram police during an attempted getaway, Mr Van Der Sypt said.

The raids capped a tense day with hundreds of troops patrolling and authorities hunting for one or more suspected extremists.

The Belgian government chose on Sunday to keep the capital on the highest state of alert into the start of the working week to prevent a Paris-style attack.

Citing a “serious and imminent” threat, prime minister Charles Michel announced that the subway, schools and universities in Brussels would be closed on Monday, preventing a return to normal in the city that is also home to the European Union’s main institutions.

Western leaders stepped up the rhetoric against Islamic State, 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 jetliner carrying 224 people in Egypt’s Sinai Peninsula. All happened within the past month.

“We will not accept the idea that terrorist assaults on restaurants and theatres and hotels are the new normal, or that we are powerless to stop them,” US president Barack Obama said in Kuala Lumpur, Malaysia.

British Prime Minister David Cameron and French president Francois Hollande, meeting in Paris, paid a quiet visit to the Bataclan concert venue, which saw the worst of the carnage in the 13 November attacks.

Authorities frantically searched for Abdeslam, who is believed to have played a key role and who crossed into Belgium the day after the attacks.

Several of the Paris attackers had lived in Brussels, including Abdelhamid Abaaoud, the plot’s orchestrator who was killed on Wednesday in a standoff with French police. Police issued a new appeal to identify the third attacker who was killed in the assault at the national stadium. They posted a photo of the man on Twitter, asking the public for information that would help identify him.

France has intensified its aerial bombing in Syria and French defence minister Jean-Yves Le Drian said the aircraft carrier Charles de Gaulle, which has been sent to the Mediterranean to help combat IS militants in Syria, will be “operational” from Monday and “ready to act”.

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, it also extended a ban on demonstrations and other gatherings through November 30, when a UN climate conference with more than 100 heads of state is scheduled to start.

(Press Association)