Al Jazeera television broadcaster, citing medical sources, reported that 61 people had been killed in clashes in Libya early on Monday.
Clashes took place overnight after an address by Saif al-Islam, son of Libyan leader Moamer Gaddafi, DPA reported.
Thousands of anti-government protesters gathered in Tripoli's Green Square, where they clashed with pro-Gaddafi protesters.
The state news agency JANA reported that people from different tribes took to the streets in the early hours of Monday expressing support for Gaddafi after Saif al-Islam's speech.