A crowd of people angry at the arrest of a rights campaigner clashed with police and government supporters overnight in the eastern Libyan city of Benghazi, a witness and local media said.
Libyan state television said separately that rallies were being held across the oil exporting country on Wednesday in support of Libyan leader Muammar Gaddafi.
The online edition of Libya's privately-owned Quryna newspaper, which is based in Benghazi, said the crowd were armed with petrol bombs and threw stones.
It said they protested outside a local government office to demand the release of the human rights activist, and then went to the city's Shajara square where they clashed with police and government supporters.
It said the rioting was now over and that government supporters had taken over the square. Fourteen people were injured including 10 police officers, but none of the injuries were serious, the newspaper said.
A Benghazi resident contacted by Reuters said the people involved in the clashes were relatives of inmates in Tripoli's Abu Salim jail, where militant Islamists and government opponents have traditionally been held.
"Last night was a bad night," said the witness, who did not want to be identified.
"There were about 500 or 600 people involved. They went to the revolutionary committee (local government headquarters) in Sabri district, and they tried to go to the central revolutionary committee ... They threw stones," he said.
"It is calm now."
Libyan state television showed footage of a rally in the Libyan capital, Tripoli, of government supporters.
Participants chanted slogans accusing Qatar-based television news channel Al Jazeera -- which was instrumental in revolts in neighbouring Tunisia and Egypt -- of broadcasting lies.