A bomb destroyed a police station in the eastern Libyan city of Benghazi early on Thursday but caused no casualties, a security source told AFP, in a second attack targeting the building.

"An explosive device was thrown at Al-Baraka police station in Benghazi, destroying what remained of the building after the bomb attack that targeted it last weekend," the source said.

"The explosion caused no casualties," he added.

An AFP journalist at the scene confirmed that the blast destroyed the building at around 7:00 am (0500 GMT).

A wave of assassinations and bombings has swept Benghazi, the cradle of the 2011 uprising against Moamer Kadhafi, in recent months.

Thursday's attack came after several weeks of relative calm in the city, where the authorities have struggled to re-establish security.

Attacks in Benghazi have generally been attributed to radical Islamists, most notably last year's September 11 assault on the US consulate that killed four Americans including ambassador Chris Stevens.

In the capital Tripoli, gunmen have been surrounding the foreign ministry since Sunday, calling for the sacking from government posts of former officials from the ousted Kadhafi regime.

On Tuesday, the groups extended their blockade to the justice ministry and gunmen briefly occupied the finance ministry on Monday.

Angry policemen also invaded the interior ministry on Sunday and Monday, demanding higher pay and promotions.

Former rebels guarding the headquarters of Libya's national television station on Sunday briefly blockaded the building, although broadcasts were uninterrupted.

The rise in violence came after a car bombing on April 23 outside the French embassy in Tripoli wounded two French security guards and caused serious damage.