BRUSSELS (AFP, REUTERS) - Belgian police arrested 16 people during a series of raids on Sunday (Nov 22) after a huge security lockdown, but Paris attacks suspect Salah Abdeslam was not among them, prosecutors said.

"Sixteen people were arrested" including one person who was injured after police opened fire on a car that drove towards police, federal prosecutor spokesman Eric Van Der Sypt told a press conference. "Salah Abdeslam was not caught during the raids," he added.

Nineteen raids were carried out in various Brussels neighbourhoods including Molenbeek - a poor immigrant district where Adbeslam is from.

Police made three other raids in the industrial town of Charleroi, where an international airport is sited.

No weapons or explosives were found in the raids, prosecutors said.

A judge will decide on Monday (Nov 23) whether to continue detaining them, they added.

The prosecutor said it was not immediately clear if the person injured in the car, which they eventually stopped in the centre of Brussels, was linked to the Paris attacks case.

Belgian Prime Minister Charles Michel announced earlier that Brussels will remain at the highest possible alert level Monday (Nov 23), with schools, universities and metros closed over a "serious and imminent" threat of attacks similar to those that struck Paris.

He said a new evaluation of the situation would be made on Monday (Nov 23) afternoon and everything was being done to return the city to normal as quickly as possible.

"What we fear is an attack similar to the one in Paris, with several individuals who could possibly launch several attacks at the same time in multiple locations," Michel told a news conference.

Belgian police urged the media and residents to respect a social media blackout during a series of police operations late Sunday (Nov 22) as security forces continued to hunt for Abdeslam, a key suspect in last week's atrocities in the French capital.

Armed officers and troops could be seen patrolling the near-deserted streets of Brussels all weekend after the government raised the terror alert to the highest level of four in the city of more than a million that is also home to the Nato and European Union headquarters.

Possible targets were malls, shopping streets and public transport, Michel had said, adding the government would boost police and army presence in the capital beyond already high levels.

Commuters trying to get to work on Monday (Nov 23) are expected to suffer delays as a result of the metro closure, though some companies had already indicated on Sunday (Nov 22) they were ready for staff to work from home.

Belgium has been at the heart of investigations into the Paris attacks on Nov 13 that left 130 people dead after links with Brussels emerged.

In France, investigators on Sunday extended into a fifth day the detention of a man arrested on Wednesday outside the building where the suspected ringleader of the Paris attacks died in a raid.

Police also released a picture of a man they said had blown himself up in the attacks and called for witnesses. Two of the Paris suicide bombers, Brahim Abdeslam and Bilal Hadfi, had been living in Belgium.

Fugitive suspected militant Salah, Brahim's 26-year-old brother, slipped back home to Brussels from Paris shortly after the attacks.

Earlier, Interior Minister Jan Jambon said Salah was not the only security threat. "It is a threat that goes beyond just that one person," he told broadcaster VRT. "We're looking at more things, that's why we've put in place such a concentration of resources."

Bernard Clerfayt, the mayor of the Brussels district of Schaerbeek, was quoted by broadcaster RTBF as saying there were"two terrorists" in the Brussels area ready to carry out violence.

Mohamed Abdeslam, the brother of Brahim and Salah, urged Salah in an interview on RTBF television to give himself up, adding that he believed Salah was still alive because he had had a last-minute change of heart while in Paris.

The mayor of Molenbeek, where the brothers lived, said there was an exchange of fire in one incident in the borough.

WITHOUT PRECEDENT SINCE WORLD WAR TWO

The government has advised the public to be alert rather than panic-stricken. People have been told to avoid crowds in the capital, while authorities have also closed museums, cinemas and shopping centres. Clubs and venues have cancelled events.

Brussels' chief rabbi Albert Gigi told Israel's Army Radio on Sunday that the city's synagogues were shut over the weekend for the first time since World War Two.

Soldiers are on guard in parts of Brussels, a city of 1.2 million people and home to institutions of the European Union and the headquarters of Nato. That said, Brussels on Sunday morning (Nov 22) resembled most other Sundays, with the normal limited number of shops, such bakeries and small supermarkets open, and many churches in the largely Catholic country still holding services. However, larger markets were shut.

The latest measures go far beyond those taken the last time Brussels was put on level four alert, for about a month at the end of 2007 and the start of 2008, when authorities intercepted a plot to free convicted Tunisian Nizar Trabelsi from a Belgian jail. Then the city closed the downtown Christmas market early and cancelled its New Year fireworks display.