Tripoli (Agencies): Arrest of a human rights activist elicited anger among hundreds of people leading to clash with police and government supporters overnight in the eastern Libyan city of Benghazi in a rare show of unrest in the oil exporting country.

The angry protesters, demanding human rights activist Fethi Tarbel’s release, threw petrol bombs, set cars ablaze and chanted "no God but God!" in clashes that left dozens injured, according to reports from the city.

Libya has been tightly controlled by leader Muammar Gaddafi for over 40 years but has also felt the ripples from popular rebellions in its neighbours Egypt and Tunisia.

Libyan state electronic media said that rallies were held in the early hours of Wednesday morning across the country in support of Gaddafi, who is Africa's longest serving leader.

Reports from Benghazi, about 1,000 km east of the Libyan capital, indicated the city was now calm but that overnight, demonstrators armed with stones and petrol bombs had set fire to vehicles and fought with police.

Gaddafi opponents used the Facebook social networking site to urge people to go out onto the streets across Libya on Thursday for what they described as a "day of rage."

Quryna newspaper, which is based in Benghazi, reported 38 people were hurt in the disputes, most of them members of the security forces. It said they had all been discharged.

"Last night was a bad night," said a Benghazi resident on a condition of anonymity.

"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 informed.

"Now, Benghazi is quiet. The banks are open and the students are going to school," the same witness said later. He added there were no reports of anyone killed in the clashes.

A videotape clip posted on the YouTube site by someone who said it was recorded in Benghazi on Tuesday night showed a crowd of people outside what looked like a government building chanting: "No God but God!" and "Corruption is the enemy of God."

Some Libyans complain about high unemployment, income disparity and limits on political freedoms, but analysts say an Egypt-style revolt are unlikely.

People in Benghazi and the area around it have a history of distrust of Gaddafi's rule. Of the hundreds of people detained in Libya over the past decade for membership of banned Islamist militant groups, many are from the city.