A fierce firefight in a Beirut housing block.

The fighting between Lebanese army soldiers and unknown gunmen broke out Wednesday night and lasted until Thursday morning.

According to a security source, two men were killed and two others were arrested when the army raided the building where the gunmen were taking shelter.

Officials at the scene said the soldiers seized weapons and ammunition inside one of the gunmen's apartment.

At least four soldiers were injured in the exchange.

The violence in neighbouring Syria has seen a spillover into Lebanon in recent days.

In the country's complex politics, the main governing party is sympathetic to Syrian President Bashar al-Assad.

But the main Lebanese opposition supports the Syrian rebels fighting for his downfall.

At least nine people have already been killed in gunbattles in Lebanon's northern city of Tripoli and in Beirut.

Travis Brecher, Reuters