Troops have been deployed across Belgium to guard potential targets of terrorist attacks, following a series of anti-terror raids and arrests.
Up to 300 soldiers will be mobilised in Brussels, Antwerp and elsewhere.
Belgium's interior minister told the BBC that his country had to make use of all the forces at its disposal.
Europe is on high alert after Islamist gunmen killed 17 people in Paris. More than 20 people have been arrested in Belgium, France and Germany.
Uniformed soldiers could be seen outside Jewish schools and government buildings in Belgium on Saturday.
Defence ministry officials said 150 police were already in place, a number that they expected to double over the course of the coming week.
The security threat level would remain raised at three - the second highest level - for at least week, they said.
Belgium launched a series of raids on Thursday evening on a group of suspected jihadists. Verviers was the site of one of the raids, where a shootout left two suspects dead.
Guns, munitions and explosives, as well as police uniforms and a large amount of money, were all seized by police during the operation. Prosecutors said the group had planned to kill police officers.
Thirteen people were arrested in total, and five people were charged on Friday with "participating in the activities of a terrorist group", prosecutors said.
"It was a possible terrorist attack, but we don't know if there were more, if this is really a network of terrorist cells in Belgium and if they're going to attack now, in the next days. Now we have to use all the forces that we have to protect us," Belgian Interior Minister and Deputy Prime Minister Jan Jambon told the BBC World Service.
"We've been investigating the data that we found in the houses that we searched, and we're investigating the suspects... and we're looking for other possible targets."
The Belgian government has also announced new measures to deal with terrorist suspects.
They include making travelling abroad for terrorist activities a crime and expanding the cases where Belgian citizenship can be revoked for dual nationals who are thought to pose a terror risk.
'Life has to go on'
There are particular concerns about the return of young Europeans who have gone to fight in Iraq and Syria.
Belgium officials say up to 350 of their citizens have gone to fight in Syria and Iraq, the highest number per capita in Europe. About 100 have returned, and are being monitored by the intelligence services, Mr Jambon said.
No link has been established between the terrorist plot in Belgium and last week's attacks in Paris on satirical magazine Charlie Hebdo, police and a kosher supermarket.
Twelve suspects are being held by police in the Paris region over last week's attacks, and France remains on its highest terrorism alert level.
Touring a market in Tulle, French President Francois Hollande said the nation had "come through the ordeal with a great deal of dignity and efficiency".
"We are of course aware that there are still threats," he said, "but life has to go on and we even need to emerge stronger".
"That's the best response we can give."
Almost 15,000 troops and police have been mobilised to provide additional security across France.
Meanwhile, one of the brothers who carried out the attack on Charlie Hebdo, Said Kouachi, has been buried in the city of Reims against the objections of city officials.
Other countries in Europe are also on high alert for potential terror threats.
Police in Germany have also arrested two men following raids on 11 properties on Friday, involving some 250 officers.
UK police have been warned to be on their guard for a terror attack against them.
In Washington on Friday, President Barack Obama and UK Prime Minister David Cameron agreed to share expertise on preventing radicalism and tackling domestic "violent extremism".