The U.N. mission in Libya said on Tuesday there was an urgent need for national dialogue and expressed grave concern at the latest violence rocking the troubled North African state.

The United Nations Support Mission in Libya statement came after violence in Tripoli and Benghazi nearly two years after the fall of the regime of dictator Moammar Gadhafi.

Libyan security forces on Tuesday defused a dozen bombs that had been placed inside a car that was parked outside a luxury hotel in the capital, the Interior Ministry said.

The incident comes a week after another hotel in the capital was thought to have been targeted by a rocket that missed and hit a nearby apartment building.

A colonel in the Libyan navy was wounded on Monday by a car bombing in central Benghazi, a security spokesman told Agence France Presse, calling the blast an "attempted assassination".

"The explosion was caused by a device attached to the car," Mohammed Hijazi said after reports of a white pickup truck exploding in the city center and bursting into flames.

Libya's premier said Monday he would restore a feared Gadhafi-era security agency and reshuffle the cabinet to help resolve a political crisis and end a wave of violence.

Ali Zeidan said he would reactivate the Internal Security Agency which helped keep the former dictator in power for decades to try to stem a spate of bombings and assassinations, particularly in the east of the country.

Two powerful explosions went off near the courthouse in Libya's second city of Benghazi on Sunday night, leaving 10 people injured and causing damage, witnesses and a security source said.

The blasts came a day after 1,000 inmates escaped during a prison riot in the restive eastern city, birthplace of the 2011 armed uprising that ousted and killed dictator Moammar Gadhafi.

Thirty-one migrants, including nine women, drowned off the coast of Libya during an attempted crossing to Italy according to survivors who managed to complete the journey, Italian media reported Sunday.

A dinghy carrying 53 migrants capsized on Friday evening, and witnesses said 31 of those who had been thrown off it drowned in the accident.

More than 1,000 inmates, mostly common law offenders, escaped during a prison riot and attack on Saturday in the restive Libyan city of Benghazi, a security official told Agence France Presse.

"There was a riot inside al-Kuifiya prison, as well as an attack from outside. More then 1,000 prisoners escaped. Special forces called in as reinforcements were given orders not to fire at the prisoners," he said, asking not to be named.

Protesters attacked offices of Libya's Muslim Brotherhood on Saturday as demonstrations sparked by a wave of assassinations in the eastern city of Benghazi turned violent, an Agence France Presse correspondent said.

Youths stormed and ransacked the building housing the Brotherhood, after hundreds took to the streets overnight to denounce the assassination of Abdessalem al-Mesmari, an anti-Islamist lawyer who campaigned for a civil state.

A marksman shot dead a prominent Libyan political activist as he emerged from Friday prayers at a mosque in the restive eastern city of Benghazi, a security official said.

Abdessalem al-Mesmari, an anti-Islamist lawyer who has been campaigning for a civil state in Libya, "was shot dead as he left a mosque and killed by a single bullet to the heart," Colonel Mohammed al-Hijazi said.

A rocket struck an apartment block in the center of the Libyan capital on Tuesday in an attack that caused no casualties, an Agence France Presse correspondent reported.

The building is located in a residential area of Tripoli between the Corinthia hotel and a tower that houses the British, Canadian and Maltese embassies, as well as foreign companies.