There has been heavy fighting outside the Libyan interim parliament in the capital Tripoli, BBC reported.
MPs fled the building after heavily armed attackers tried to storm it. Some eyewitnesses say the gunmen were from the powerful Zintan Brigade of former rebel fighters.
However a spokesman for a retired general, Khalifa Haftar, claimed his forces had carried out the assault.
Authorities are 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.
The situation in Tripoli remains unclear, with some reports suggesting parliament had advance warning of the attack and suspended its session.
Other local reports suggest some MPs may have been taken hostage.
Gen Haftar's forces on Friday launched a major air-and-ground attack against Islamist militants in the eastern of Benghazi, prompting the government to declare a no-fly-zone there.
At least 70 people died in the fighting.