Libyan Prime Minister Abdurrahim al-Keib has branded gunmen who attacked his office in the capital Tripoli as "outlaws".
In a televised speech he said the men had "pretended" to be rebel fighters to claim cash handouts offered as rewards for helping to topple Col Gaddafi, BBC reported.
One security guard was killed when about 200 armed men, some carrying mortars, tried to storm the building.
They were eventually repelled by security forces.
"This afternoon, the building of the council of ministers came under attack by outlawed gunmen pretending to be revolutionaries, but they are not," said Mr Keib.
"These outlaws claimed that their attack was for getting some cash allocated as rewards for the real revolutionaries."
He added: "As the government asserts that it will deliver on its promises, it also announces that it will not give in to blackmail or to outlaws and will not negotiate under the threat of force."
Three other security guards and one of the gunmen were also injured in the battle, Tripoli security official Khaled Besher said.
Fourteen of the attackers had been arrested, he added.