It is also said that security forces and pro-government militias used live ammunition to disperse a peaceful demonstration by the youth.
Two pro-democracy protesters were also killed and dozens more injured in clashes with police in Benghazi city.
Protests broke out in the city of Benghazi on Tuesday night following the detention of a human rights activist who was an outspoken opponent of Libyan President Muammar Gaddafi.
Security forces fired tear gas and used water cannons to break up the demonstrations and arrested scores of opposition supporters.
At least 40 people were wounded during clashes between supporters of Gaddafi and pro-democracy protesters, the medics said.
Libyans, who have been emboldened by recent revolutions in Tunisia and Egypt that unseated two authoritarian regimes, vowed to continue rallies on Thursday called the “Day of Anger.”
On Wednesday pro-government rallies were held in support of Libya's long-time leader.
Meanwhile, human rights group Amnesty International has urged the Libyan government to stop its crackdown on peaceful demonstrations.
"The Libyan authorities must allow peaceful protests, not try to stifle them with heavy-handed repression," said Malcolm Smart, Amnesty International's director for the Middle East and North Africa on Wednesday.
"Libyans have the same rights as Egyptians and Tunisians to express discontent and call for reform in their own country," Smart added.
The group also called on Libya to recognize and respect the rights of the pro-democracy Libyans.
Britain and the European Union have urged the Libyan government to avoid violence and demanded that it allow “free expression.”
Gaddafi came to power 41 years ago during a military coup. Sources say he has held emergency meetings with the country's top officials over fears of massive protests that are sweeping to Libya now and threaten one of the longest serving rulers in history.
Reports say that underground opposition groups and civil society movements are planning to hold mass pro-democracy protests in major cities across the African country in the coming days.
End item/ 159