Retired General Khalifa Haftar has claimed responsibility for an armed attack on the Libyan parliament in Tripoli.
His group has been engaged in fighting militant Islamists in the eastern city of Benghazi.
The gunmen launched their assault on parliament in armoured vehicles. Black smoke rose above the building as militiamen loyal to the government responded.
The government is struggling to contain militias that control parts of Libya.
A planned new constitution remains unwritten and the country has had three prime ministers since March.
General Haftar, a former rebel in the war against Colonel Gaddafi, had already sent his fighters into Benghazi on Friday against Islamists based there, claiming Libya's government had failed to halt violence in the eastern city.
At least 40 people were killed in those clashes.