Belgian prosecutors announced early today that police had detained 16 people in 22 raids related to the Paris attacks, but that the 26-year fugitive Salah Abdeslam was not among them.
Authorities continued to maintain their highest terror alert in the capital Brussels for a third straight day.
Federal prosecutor Eric Van Der Sypt said 19 raids were carried out in Molenbeek 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,'' Van Der Sypt said. ''The investigation will be relentlessly continued.''
One of those detained was injured when a car he was in tried to hit the police during an attempted getaway, Van Der Sypt said.
The raids capped a tense day with hundreds of troops patrolling and authorities hunting for one or more suspected militants, as the Belgian government chose Sunday to keep the capital on the highest state of alert into the start of the workweek to prevent a Paris-style attack.
Citing a ''serious and imminent'' threat, Prime Minister Charles Michel announced that schools and universities in Brussels will be closed today, with the subway remaining shut down, in the city that is also home to the European Union's main institutions.
''We fear an attack like in Paris, with several individuals, perhaps in several places,'' Michel said after chairing a meeting of Belgium's National Security Council.
While Brussels was kept on the highest of four alert levels, the rest of the country remains on a Level 3 alert, meaning an attack is ''possible and likely''.
''Nobody is pleased with such a situation. Neither are we. But we have to take our responsibility,'' Michel said.
Western leaders stepped up the rhetoric against the Islamic State group, which has claimed responsibility for the attacks in Paris that killed 130 people and wounded hundreds more (See: France under emergency: terrorists kill over 120 in multiple attacks); 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 (Russian airliner crash: search continues, IS claims downplayed). 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,'' President Barack Obama said in Kuala Lumpur, Malaysia.
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,'' Le Drian said. ''That's the only possible direction.''