Grenade attacks targeting Libya's intelligence headquarters have led to a series of clashes between rival military groups in Tripoli.

Sunday's gun battle between two rival groups left the building partially destroyed and at least five people injured.

"The number of casualties since yesterday is around five cases. We received the latest case this morning -- it was a doctor who had just ended his shift and just as he was leaving he was hit with shrapnel in his chest," Ezz Eddin Ahmad, a local doctor, told the Reuters news agency.

Nearby shops have also been looted in the continued fighting.

Elsewhere on Sunday, a car exploded outside a police station in Libya's second largest city Benghazi, causing damage to the building and wounding three policemen, according to an AFP news agency photographer and witnesses.

The attacks came as the country's new authorities tried to empower the national army and police but struggle to rein in armed groups born out of the 2011 conflict that toppled long-time leader, Muammar Gaddafi.

The blast occurred before dawn at a police station in the Hadaiq neighbourhood, damaging the entrance of the building, unhinging a door and shattering windows.

The facades of nearby shops were also damaged. The charred remains of the vehicle remained at the scene.

"Several suspects have been arrested," Ezzedine al-Fazzani, a spokesman for the interior ministry in the east, told AFP news agency.

He said there had been "no fatalities, only minor injuries".

Ashraf Eid, a Libyan officer, told the Reuters news agency that incident took place at around 5:10am local time.

"A green car, model Daewoo, parked outside the police office then we heard someone open the car door... After a while the same car passed by us and we saw a bearded man inside and the explosion happened a short time after that man who was inside the car disappeared.

"It's a huge explosion which obviously can be considered a terrorist attack," said Eid.

The Mediterranean city of Benghazi, centre of the 2011 uprising against Gaddafi, has witnessed several blasts, while a September 11 attack by fighters on the US mission in Benghazi killed four Americans, including ambassador Chris Stevens.

The city has also witnessed a wave of assassinations, targeting officials with links to the former regime, which is widely blamed on hardline Islamists.

Source: Agencies