Two people have been killed in a "counter-terrorism" raid in Verviers in eastern Belgium and the security alert level has been raised in the country, according to a Belgian prosecutor.

Magistrate Eric Van der Sypt told reporters in Brussels on Thursday that the suspects were on the verge of committing a major attack, and that they immediately opened fire on security forces.

He said in an emergency news conference that raids were under way in the Brussels region and Verviers.

"Belgium's terror alert level was raised to its second highest level," he said.

Local media reports said there were no casualties among the security forces involved.

Police closed the streets around the building where the operation was taking place, national La Libre newspaper said.

Germany has also conducted a series of raids in Berlin and have taken two men into custody on suspicion of recruiting fighters and procuring equipment and funding the Islamic State of Iraq and the Levant armed group.

At least 11 residences were raided by 250 police officers in the German capital. The Belgian prosecutor said at a press conference on Friday that 13 people were detained.

France's Prime Minister Manuel Valls said on Friday that there was no "direct link" between anti-terror raids in Belgium and last week's attacks in Paris.

'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 comes a week after the deadly attacks in Paris that killed 17 people, including journalists and police officers.

Al-Qaeda's Yemen branch claimed responsibility for the attacks in Paris on the Charlie Hebdo newspaper.

Belgian investigators said earlier on Thursday they were probing whether an arms dealer sold weapons used in the Paris attacks, after Amedy Coulibaly, one of the Paris gunmen, sold the man a car belonging to his partner Hayat Boumeddiene.