Belgian police have 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.

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," Van der Sijpt told a news conference on Friday.

The group was on the verge of carrying out terrorist attacks to kill police officers in public roads and in police stations.

Eric Van der Sijpt, Belgian Public Prosecutor spokesman,

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.

'Gunshots and explosions'

Witnesses said gunshots and several explosions were heard on a residential street in the Belgian city of Verviers near the railway station.

"I heard a sort of explosion, followed by several gunshots," one local told RTBF.

"For the moment, I cannot tell you any more, because I do not dare go out to see what is happening."

Another local resident was quoted as saying that "machineguns were firing for about 10 minutes".

The incident came a week after the deadly attacks in Paris that killed 17 people, including journalists and police officers.

Across western Europe, French, German, Belgian and Irish police had at least 30 suspects behind bars as anxiety soared in the wake of last week's bloody spree in and around Paris.

In Ireland, police arrested a suspected French-Algerian militant at Dublin Airport as he tried to enter the country using a false passport. The man, who was being interrogated, landed on a European watch list after expressing support in social media for last week's attacks.

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.

Source: Agencies