Belgium has ordered its army into the streets and "anti-terror" raids across Western Europe have netted dozens of suspects as authorities rushed to thwart more attacks by people with links to armed groups.
French, German, Belgian and Irish police had at least 30 suspects behind bars on Friday and in Brussels, authorities said a dozen searches led to the seizure of four Kalashnikov assault rifles, hand guns and explosives.
Several police uniforms were also found, which Belgian authorities said suggested the plotters had intended to masquerade as police officers.
Belgian police arrested 13 people during a dozen raids overnight, foiling a plot to kill police officers "in public roads and in police stations", prosecutors have said.
The arrests camafter two suspects were shot dead in a gun battle during one of the police raids in the eastern town of Verviers on Thursday night.
Five of those arrested were later charged with "participating in the activities of a terrorist group", federal prosecutors' spokesman Eric Van der Sijpt told AFP.
The group was on the verge of carrying out terrorist attacks to kill police officers in public roads and in police stations.
"The group was on the verge of carrying out terrorist attacks to kill police officers in public roads and in police stations," Van der Sijpt told a news conference on Friday.
Police found Kalashnikov assault rifles, explosives, ammunition and communications equipment - along with police uniforms that could have been used for the plot, he said.
Belgium will also seek the extradition of two Belgian suspects from France, although there is no link seen with last week's Paris attacks, prosecutors said.
"I can confirm that we started this investigation before the attacks in Paris," Van der Sijpt said.
The "important arrests" meant that "not only a terror cell but also their support network" have been dismantled, he added.
"Belgium's terror alert level was raised to its second highest level."
France's Prime Minister Manuel Valls also confirmed that there was no "direct link" between anti-terror raids in Belgium and last week's attacks in Paris.
Local media reports said there were no casualties among the security forces involved.
Germany also conducted a series of raids in Berlin and took two men into custody on suspicion of recruiting fighters and procuring equipment and funding the Islamic State of Iraq and the Levant (ISIL) armed group.
At least 11 residences were raided by 250 police officers in the German capital.
Al-Qaeda in the Arabian Peninsula - the armed group's Yemen branch - claimed responsibility for the attacks in Paris on the office of satirical magazine Charlie Hebdo.