Central Brussels was almost empty on Saturday night as a terror alert led restaurants and bars to shut early amid fears of a Paris-style attack.

Soldiers patrolled the streets as a manhunt continued for the fugitive Salah Abdeslam, who was thought to be armed with a suicide belt.

Reports said he was in the Brussels area and trying to get to Syria.

The city was a base for the attackers - Islamic State militants - who killed 130 people in Paris.

Belgian Prime Minister Charles Michel said there was "quite precise information" that "several individuals with arms and explosives could launch an attack... perhaps even in several places".

Abdeslam appeared to have a large jacket and may have been ready to blow himself up, one of the men who drove him to Belgium has told his lawyer.

Carine Couquelet told Belgian TV this raised questions, including the possibility that Salah Abdeslam may have been supposed to blow himself up in Paris but had had second thoughts.

Friends of Abdeslam told ABC News they had spoken to him on Skype and said he was hiding in Brussels and desperately trying to get to Syria.

They said he was caught between European authorities hunting him and so-called Islamic State members who were "watching him" and were unhappy that he had not detonated his suicide belt.

The Belgian authorities responded by placing Brussels on its highest level of alert.

Residents were told to avoid crowds, the metro was closed along with cinemas and shopping malls, cafes and restaurants were asked to shut at 6pm and soldiers deployed on the streets.

The US embassy told Americans in the country to stay indoors and the US European Command issued a 72-hour restriction on travel to the city by all military personnel and contractors.

The government would review the security situation in Brussels on Sunday afternoon, Michel said.

(BBC)