Sixteen people have been arrested in a series of co-ordinated police raids in Brussels and Charleroi on Sunday night - but Paris terror suspect Salah Abdeslam remains at large.

The Belgian federal prosecutor Eric Van Der Sijpt said 19 raids were carried out in Molenbeek, Jette, Anderlecht, Schaerbeek, Forest and Woluwe-Saint-Lambert. Three other raids were made in Charleroi.

He said no arms or explosives were found, adding: "No further information can be given about objects found nor about the identity of the persons arrested."

The terror threat level in the Brussels region has been maintained at level 4, the highest possible, Belgian prime minister Charles Michel announced on Sunday.

Schools in the Brussels region - including European schools - will be closed on Monday, and metro and underground tram services will not operate until at least Monday afternoon when a further evaluation of the situation will be made, Michel said.

At a press conference on Sunday evening, the prime minister reiterated that the threat remained "serious and imminent". The alert level in the rest of Belgium remains level 3 out of 4.

Some big Belgian firms have urged their staff to work from home on Monday. The European institutions will remain open. Flexible and home working are encouraged wherever possible, Commission vice-president Kristalina Georgieva wrote on Twitter.

A telephone hotline (1771) set up to provide information to worried residents about the terror threat level received 400 calls per hour on Saturday. Most of the calls were enquiring about cancelled events and closures. A team of 20 people are manning the lines.

Terror threat 'broader than Abdeslam'

The terror threat currently facing Belgium is "broader than Salah Abdeslam alone", interior minister Jan Jambon said in a VRT interview on Saturday night. "There are several suspects - that is why we have concentrated so many of our resources on this," he said. "We are following the situation minute by minute. There is a real threat, but we are doing everything we can, day and night."

Abdeslam's brother urges him to surrender

The brother of the on-the-run Paris terror attacks suspect Salah Abdeslam said on Sunday his family "would prefer to see him in a prison than in a cemetery". Mohamed Abdeslam made a public plea for his brother to surrender himself to police "so that he can give us answers - to the family but also the families of victims".

Third suspect in custody

A third suspect detained by Belgian authorities over the Paris terror attacks has been named as Abraimi Lazez, a 39-year-old man of Moroccan descent born in Belgium and living in the Brussels region. Lazez was arrested in his car in Laeken on Thursday. Three or four weapons were found at his home in Molenbeek, and two more in a van belonging to him. He will appear before a judge on Wednesday.

'Two men' sought by Brussels police

According to Le Soir, investigators in Brussels are looking for at least two men, one of whom could be carrying a bomb similar to that used in the Paris suicide attacks. The paper said: "All the terrorists who died in Paris were wearing one. It seems coherent to believe that the fugitive still has his." Le Soir added that investigators were "worried that other terrorist cells would spring into action" and that there could exist other "active accomplices" in Brussels.

Salah Abdeslam extremely volatile

Salah Abdeslam, the man wanted by police in connection with the Paris terror attacks, returned to Brussels "extremely annoyed and maybe ready to blow" himself up, according to the lawyer of one of the men accused of helping him flee France for Belgium. Carine Couquelet, who represents 21-year-old Hamza Attou, who has been charged over the attacks, said in an interview for French TV news channel LCI: "My client was very scared. He has not mentioned the presence of firearms [on Abdeslam], but a big jacket, possibly with an explosive belt. According to recent statements by my client, Salah was extremely upset and maybe ready to blow."

Photo: Sander de Wilde/Demotix/Corbis