Officials say former Libyan rebels have launched an attack on the prime minister's office in the capital Tripoli, leaving at least one guard dead.
They said about 200 armed men, some carrying mortars, tried to storm the building but were repelled by security.
Four others were wounded in the clashes, which lasted several hours.
The attackers - ex-rebels who fought to topple Col Gaddafi last year - were demanding pay-outs promised under a reward scheme suspended last year.
Sources said that although Prime Minister Abdurrahim al-Keib was in the building at the time he is safe.
Most people inside the building fled, including the finance minister and the deputy prime minister.