At least one person has been killed and 20 others injured in the eastern Libyan city of Benghazi after police and demonstrators stormed militia bases, al Jazeera television reported.
The violence comes after some 30,000 people marched through the city on Friday demanding an end to armed groups.
Libya's interim authorities have been attempting to rein in the numerous groups, which are said to have played a key role in helping topple the regime of long-time ruler Muammar Gaddafi last year. There have been reports of miltias carrying out abductions and killings.
The bases stormed on Friday include the headquarters of the Islamist group Ansar al-Sharia, which is suspected of staging attack on a U.S. consulate in Benghazi, in which U.S. Ambassador to Libya Chris Stephens and three other embassy staff were killed.
The attack came amid protests over a U.S.-produced film deemed insulting to Islam.
The group has denied any involvement in the killing of the four Americans.
Demonstrators chanted "No more al-Qaeda!" and "The blood we shed for freedom shall not go in vain!" as they broke into the Ansar al-Sharia compound on Friday night, evicting fighters and setting a vehicle on fire.
Fighting was also reported outside the headquarters of the Rafallah Sehati brigade.