Heavy clashes between rival armed groups erupted in eastern areas of Libya's capital Tripoli on Thursday evening, local residents said.
The clashes broke out first in the Suq al-Juma district and soon spread across all the eastern areas of the capital, with anti-aircraft artillery used in some areas.
Head of Tripoli-based Supreme Security Committee Hashem Bishr said that the clashes were between fighters from Misrata militia and local armed groups.
The Misrata militia reportedly entered the capital to take revenge for one of its commanders Nuri Friwan, who was wounded during a shootout on Tuesday and later died in hospital.
The security situation was deteriorating in Libya especially after abduction of Libyan Prime Minister Ali Zeidan in early October.
In response to Zeidan's request for help, NATO announced on Tuesday that an advisory team would soon be set up in Libya to help address the security issues.