A bomb exploded at a courthouse in the Libyan city of Benghazi on Friday April 27, wounding four people and damaging nearby buildings in a new challenge to the government's struggle to restore order, Reuters reported.

A security official said three explosive devices were planted near a courthouse wall. The blasts shattered windows of a nearby hospital, wounding one person inside.

The explosion left gaping holes on the side of the courthouse in the centre of Benghazi, and shattered the windows of the building as well as a nearby office block.

Security guard Ashour al-Farsi said the blast was set off around four in the morning. "We heard huge booms and rushed out to see what it was," he told Reuters. "That's when the glass shot through my leg," he said, adding that two other security guards were also hurt.

Residents of Benghazi, the cradle of Libya's revolution, have voiced frustration at being all but forgotten by the new leadership in Tripoli since Muammar Gaddafi was ousted in August.

In late January, protesters stormed the local headquarters of the ruling National Transitional Council (NTC), smashing its windows with stones and metal bars. On April 10, a home-made bomb was thrown at a convoy carrying the head of the United Nations mission to Libya but no one was hurt.

Hampered by the lack of an effective national army or internal security force, the NTC is grappling to disband dozens of powerful militias that effectively control various parts of the country.

Militia chiefs have resisted attempts to integrate their personnel into the official military and police forces.