Four people were killed when security forces clashed with armed demonstrators outside a police station in the eastern Libyan city of Benghazi on Thursday, security sources said.

Two special forces soldiers, one Islamist militiaman and a civilian were killed in the incident, the sources said.

They added the violence was believed to be linked to the recent detention of two men in connection with several assassinations of security officials in the country's second city.

About 10 people were wounded in the violence, including two badly injured policemen, hospital officials said. Colonel Salah Buhlaiga, the head of special forces in Benghazi, told Reuters he was one of the wounded.

Trouble broke out late afternoon when a crowd of people believed to be Islamists gathered outside the police station in the al-Hawari district to protest against the reported transfer out of Benghazi of the two detained men suspected in the recent killings.

Hand grenades were thrown at the police station, and then armed men appeared and fired automatic weapons at the building, triggering a gunfight with police and special forces in which the four were killed, the sources said.

Benghazi, the North African country's second biggest city, was where the anti-Qadhafi uprising broke out but is now a hot spot for violence, riven with armed factions.

In September, the US ambassador to Libya and three other Americans were killed in an attack on the US diplomatic mission in Benghazi, the worst of a string of attacks on international convoys and official buildings in the city.

Last month, Benghazi's police chief was shot dead, the latest in a series of killings, and ensuing attacks on police stations underline the scale of the challenge facing the authorities.

On Sunday, unknown assailants fired a rocket-propelled grenade at a Benghazi police compound that houses patrol cars, damaging an office and killing one police officer. A gun battle followed and three of the police reinforcements who arrived at the scene were killed, a police spokesperson said.