Heavy shooting from guns and anti-aircraft weapons could be heard early on Tuesday in the Libyan capital Tripoli, Reuters witnesses said.
Fighting erupted between militias in the eastern Suq al-Juma area, said a militia source with government ties, adding that he had no further information.
A Facebook website showed what it said were two burned-out cars though Reuters could not verify its authenticity.
An interior ministry official said he had no information about the shooting, when contacted by Reuters. A defence ministry official declined to comment.