Brussels is on its highest level of terror alert in response to information about the risk of an attack like the one in Paris last week, Belgian Prime Minister Charles Michel says.
Police and military officers patrolling in central Brussels on Saturday. Photo: AFP
A week after Paris bombings and shootings carried out by Islamic State militants, Brussels was placed on the top level "four" in the government's threat scale after a meeting of police, justice and intelligence officials.
Soldiers were 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.
Mr Michel said the fear was that "several individuals with arms and explosives could launch an attack... perhaps even in several places".
Some of the attackers who killed 130 people in Paris lived in Brussels and leading suspect Salah Abdeslam, the focus of a huge manhunt, is believed to have gone back to Belgium.
The Brussels metro is closed till Sunday and people have been told to avoid crowds.
These include shopping centres and concerts, and the authorities have also recommended that large events, including football matches, be cancelled, a statement said.
The warning for the rest of Belgium stays at a lower level, which is still at a "serious" level.
The Belgian government will review the security situation in Brussels on Sunday afternoon.
Interior Minister Jan Jambon earlier told reporters the country's situation was "serious", but "under control", as he arrived for a special security cabinet meeting on Saturday.
In Paris, French police have freed seven people arrested during the massive raid on an apartment housing the suspected instigator, Abdelhamid Abaaoud, prosecutors said according to AFP news agency.
Abdelhamid Abaaoud was killed in the raid in the Paris suburb of Saint-Denis.
However, Jawad Bendaoud - who has admitted lending the apartment to two people from Belgium "as a favour", but denied knowing any more - is being held in custody.
Rescuers and police cordon off the area close to Rue Bichat, a site of one of the attacks in Paris on 13 November in which 129 people were killed. Photo: AFP
Belgium at heart of Paris attack probe
Belgium has been at the heart of investigations into the Paris attacks - which included suicide bombers targeting a France-Germany soccer match - after the links to Brussels, and the poor district of Molenbeek in particular, emerged.
Fugitive suspected militant Salah Abdeslam, 26, slipped back home to Brussels from Paris shortly after the attacks, in which his elder brother Brahim blew himself up at a cafe. Fears of the risks he still poses prompted the cancellation last week of an international friendly soccer match in Brussels against Spain.
A second man from Molenbeek, Bilal Hadfi, was also among the Paris suicide bombers.
Three people detained in Brussels are now facing terrorism charges. Federal prosecutors said on Saturday that weapons had been found at the home of a person charged on Friday.
Mr Jambon told reporters he wanted a register of everyone living in Molenbeek because it was not clear at present who was at each address, a process local officials had already started.
EU interior and justice ministers in Brussels on Friday pledged solidarity with France and agreed a series of new measures on surveillance, border checks and gun control.
French authorities have said the attacks were planned in Brussels by a local man, Abdelhamid Abaaoud, 28, who fought for Islamic State in Syria and was killed in a police siege of an apartment in the Paris suburb of St. Denis on Wednesday.
Abaaoud's fingerprints were found on one of three AK47 assault rifles in a car left in eastern Paris, a source close to the investigation said, though it was not clear if he took part in the attacks or had just handled the weapon at some point.
A Belgian man of Moroccan descent, Ahmad Dahmani, 26, has been arrested at a luxury hotel in Antalya along with two other terror suspects, Turkish authorities have told the BBC.
He is believed to have been in contact with the suspects who perpetrated the Paris attacks, an official said. He arrived from Amsterdam on 14 November; there is no record of the Belgian authorities having warned Turkey about him, which is why there was no entry ban, the official said.
The last time any part of Belgium was put on maximum alert was in May 2014 when an Islamist gunman shot dead four people at the Jewish Museum in Brussels. At that time, Jewish schools, synagogues and other institutions were put on level four.
- BBC / Reuters / AFP