Soldiers have fanned out to guard possible terror targets across Belgium, including some buildings in the Jewish quarter of the port city of Antwerp.
It is the first time in 30 years that authorities have used troops to reinforce police in Belgium’s cities, a day after anti-terror raids netted dozens of suspects across western Europe.
Belgium has increased its terror warning to level three, the second highest, following the anti-terror raids on Thursday which left two suspects dead.
Thirteen people were detained in Belgium and two in France in an anti-terror sweep following a gunfight in which two suspected terrorists were killed.
Authorities said a dozen searches in the Belgian city of Verviers led to the discovery of four military-style weapons including Kalashnikov assault rifles.
Investigators also found several police uniforms during the raids, which could have allowed the suspects to pass themselves off as police officers to launch an attack.
It comes after police moved in on a suspected terrorist hideout at a bakery in the eastern city, killing two suspects and wounding and arresting a third. The arrested suspect was charged with belonging to a terrorist organisation.
Unlike the Paris terrorists, who attacked the office of a satirical newspaper and a kosher grocery store, the suspects in Belgium were reportedly aiming at hard targets: police installations.
Eric Van der Sypt, a federal magistrate, said the terrorists were aiming to kill police on the street or in their offices.
“As soon as they thought special forces were there, they opened fire,” he said. “They were on the verge of committing important terror attacks.”
Across Europe, anxiety has grown as the manhunt continues for potential accomplices of the three Paris terrorists, all of whom were shot dead by police. Authorities in Belgium signalled they were ready for more trouble by raising the national terror alert level from two to three.
“It shows we have to be extremely careful,” Mr Van der Sypt said. The Verviers suspects “were extremely well-armed men” equipped with automatic weapons, he added. Authorities have previously said 300 Belgian residents have gone to fight with extremist Islamic groups in Syria. It is unclear how many have returned.
Prime minister Charles Michel said the increase in the threat level was “a choice for prudence”. “There is no concrete or specific knowledge of new elements of threat,” he said.
The suspects in Verviers opened fire on police when officers closed in on them near the city’s railway station, the magistrate said. There was an intense firefight for several minutes.
Video posted online showed a dark view of a building amid blasts, gunshots and sirens, and a fire with smoke billowing.
No police were wounded or killed in the clash at the height of the evening rush hour in a crowded neighbourhood of the former industrial city of 56,000, about 80 miles south east of the capital Brussels.