By Danny Kemp and Lachlan Carmichael
Brussels is set to remain under security lockdown as Belgian police arrested 16 people in a wave of anti-terrorism raids.
Schools and the metro are shut on Monday (local time) as Brussels stays at the highest possible alert level over what Belgian Prime Minister Charles Michel called a "serious and imminent" threat of attacks similar to those that killed 130 people in France.
Officials will review the situation again later on Monday.
Police on Sunday carried out 19 raids in Brussels and three in the industrial town of Charleroi, detaining 16 people, prosecutors said, while the driver of a car was injured after police fired two shots when the vehicle drove at officers.
"Salah Abdeslam was not caught during the raids," federal prosecutor spokesman Eric Van Der Sypt told a press conference just after midnight, meaning Europe's most wanted man remains at large.
Armed officers and troops have been patrolling the near-deserted streets of the tense Belgian capital all weekend after the government raised the terror alert to the highest level of four in the city.
The European Union and NATO, which are based in Brussels, both said they would increase security and urged non-essential staff to work from home on Monday.
Michel said the Brussels metro system would remain shut, and schools and universities would be closed over concerns that jihadists were planning a repeat of the Paris gun and suicide bombing attacks on November 13.
He said the rest of the country, including Brussels airport, would remain on security alert level three, meaning an attack is considered possible and the threat credible.
The historic Grand Place square in central Brussels, usually bustling, was virtually empty at the weekend, as anxious residents heeded warnings to stay home.
With a massive manhunt on for several suspects linked to the carnage in Paris, Belgian police urged the media and social media not to show live footage of the police operations taking place on Sunday evening.
Many Belgians responded in light-hearted fashion by tweeting pictures of cats under the hashtag #BrusselsLockdown.
French police meanwhile released a photo of the third of three men who blew themselves up outside France's national stadium during the rampage, which also targeted the Bataclan concert hall as well as a string of bars and restaurants.
The man in the picture passed through Greece with one of the other suicide bombers, carrying a Syrian passport in the name of Mohammad al-Mahmod, a source close to the investigation said.
With the world on edge over the jihadist threat, US President Barack Obama said the most powerful tool in the fight against IS was to say "that we're not afraid".
He added that he would go ahead with a December visit to Paris for UN climate talks and called on other countries to show similar resolve.
French President Francois Hollande will embark on a diplomatic offensive in the coming days in a bid to forge a broad anti-IS coalition.
He will host Britain's David Cameron on Monday before meeting Obama in Washington on Tuesday, holding talks with Germany's Angela Merkel in Paris on Wednesday and Russia's Vladimir Putin in Moscow on Thursday.
Meanwhile, Eagles of Death Metal, the Californian band that was playing at the Bataclan where 89 people were massacred, spoke for the first time since the attacks, with singer Jesse Hughes saying many fans died trying to protect their friends.
"So many people put themselves in front of people," he said in an excerpt of an interview with Vice.com.