Charles Michel said the fear was that "several individuals with arms and explosives could launch an attack... perhaps even in several places".   

But he told the press conference: "We urge the public not to give in to panic, to stay calm.

"We have taken the measures that are necessary."

The Belgian Prime Minister Charles Michel has just held a press conference.

He said that the decision to raise the terror alert was "based on quite precise information" of the risk of attack.

The government will review the situation on Sunday afternoon, he added.

Last night marked a week since the Paris attacks. 

Crowds gathered near the sites where terrorists struck, with many heading to the Place de la Republique to remember the victims. 

Dozens of French artists and cultural figures had urged people to make a lot of "noise and light" at 21:20 local time (20:20 GMT) to mark the exact time the attacks began. 

Here are some of the pictures from the scene: 

Image source, Reuters

Image source, EPA

Image source, AP

Image source, AFP/Getty

Belgian Interior Minister Jan Jambon says the country's situation is "serious'' but under control, with the nation at its highest state of alert - level 4/4.

Mr Jambon told reporters as he arrived for a special security cabinet meeting that "the situation is serious", adding: "Otherwise we would not go to level 4, but the situation is under control."

Image source, Reuters

Belgian soldiers stand guard outside the Radisson Blu hotel in central Brussels today.

A hotel belonging to to the same group was attacked in the Malian capital Bamako on Friday, killing 19 people.

The British Foreign Office has updated its travel advice for Britons visiting Belgium , externalin the light of the raised terror threat in Brussels. 

The advice cautions against visiting crowded places

Asia-Pacific leaders meeting in Malaysia today have condemned the series of Islamic extremist attacks from Paris to Mali, urging an international effort to fight the scourge. 

Prime Minister Najib Razak of Muslim-majority Malaysia strongly denounced the ideological justification for violence claimed by militants. 

"The perpetrators of these cowardly and barbaric acts do not represent any race, religion or creed," he told fellow Southeast Asian leaders. "They are terrorists." 

The Molenbeek district of Brussels has been thrust into the international spotlight following the Paris attacks, with Belgian authorities carrying out a series of raids searching for key suspects thought to have lived in the area. 

Two of those arrested have been charged with terrorist offences. 

This has led to Molenbeek being labelled as a jihadi haven - but some residents say that is an unfair description. 

The BBC's Alex Forsyth has taken a look at the area - you can read the report here.

Here's some more from our correspondent James Reynolds, in Brussels.  

After a string of attacks in recent years linked to its grimy streets in central Brussels, a key question arises, the AP news agency says: Why Belgium? 

The tiny nation renowned for beer, chocolates and the comic book hero Tintin is now suddenly notorious for Islamic extremism - and the ready availability of illegal weapons, AP says.

Thee are other factors too: Belgium has a central location in Europe; few border controls; a common language with prime jihadist target France; and a political divide between French and Dutch speakers that has long created bureaucratic disarray in justice and security, AP says  

The Belgian government has recommended the cancellation of professional soccer games scheduled over the weekend, and that the 19 communes that make up the Brussels region consider canceling all other major events due to take place, AP reports.

Image source, AP

Patrols had already been taking place in Belgium in light of last week's Paris attacks. This picture shows soldiers from the Belgian army walking among members of the public in the Grand Place, Brussels, on Friday. 

Image source, EPA

Belgium's interior minister, Jan Jambon, is among ministers who have arrived at an extraordinary State National Security Council in Belgium this morning, after the terror alert status was raised to the highest level. 

Belgian authorities have so far charged three people with involvement in the attacks.  

Turkish police have detained a man suspected of scouting out target sites for IS ahead of last week's attacks in Paris, Reuters is reporting, citing the Dogan news agency. 

 Ahmet Dahmani, 26, a Belgian man of Moroccan origin, is said to have been detained at a hotel in Antalya. 

 Dogan is reporting that two other men, who are both Syrian citizens, were detained nearby and are suspected of having been sent by IS to make sure Dahmani safely crossed the border. 

Counter-terrorism police first became aware of him when he arrived on a flight to Antalya, and he was then tracked to the hotel, Dogan said.

The BBC's Europe correspondent James Reynolds, in Brussels, said: "If people choose to leave their homes, they won't have many ways of getting around on public transport as, of course, the metro system is closed.

"The government has issued instructions via its crisis centre. Interestingly, it said: 'Please, people - do not spread rumours. Follow official information by the authorities and by the police'. 

"The government says it will say more on Sunday."

We'll be bringing you updates throughout the day, following last Friday's attacks in Paris that left 130 people dead.

Here are the latest developments:

• Belgium has raised its terror alert in the Brussels region to the highest level and is warning of a "very serious" and "imminent" threat
• The metro in the city will be closed until at least Sunday and members of the public have been warned to avoid crowds, including shopping centres and concerts
• Brussels was home to the suspected perpetrators of the Paris terror attacks, in which 130 people died
• The warning for the rest of Belgium remains at a lower threat level
• Salah Abdeslam, one of those still being sought over the Paris attacks, is believed to have returned to Belgium
• The UN Security Council has unanimously adopted a resolution to "redouble" action against so-called Islamic State (IS)