A rogue Libyan ex-general resumed air strikes on jihadists in the city of Benghazi Wednesday, while gunmen attacked an interior ministry team in Tripoli tasked with protecting the outgoing government.

Amid the ever-worsening insecurity in the North African country, Washington urged US citizens there to leave "immediately" and was even readying a possible evacuation of its embassy.

And outgoing premier Abdullah al-Thani said he would ask a court to decide whether he must turn over power to his successor, whose election by parliament some have called illegal.

Air forces loyal to former general Khalifa Haftar attacked a jihadist camp on the outskirts of Benghazi, cradle of the 2011 uprising that ousted dictator Moamer Kadhafi, ex-rebels told AFP.

"A warplane carried out raids on a camp of the 'February 17 Martyrs Brigades,' hitting it with two missiles," said Ahmed al-Jazaoui, without reporting casualties.

Haftar, who returned to Libya from American exile to join the revolution against Kadhafi, launched an anti-jihadist campaign in Benghazi on May 16 when warplanes also bombed February 17 positions.

Subsequent fighting killed at least 79 people, prompting the government to accuse Haftar of being an "outlaw" and declare Benghazi a no-fly zone.

The powerful February 17 brigade is made up of Islamist ex-rebels, including radicals, and is suspected of links with Ansar Al-Sharia, a group classified as a terrorist group by Washington.

On the political front, the cabinet office condemned an attack late Tuesday on an interior ministry force in charge of protecting the government, in which there were no casualties.

The incident was the work of "outlaws," Thani's government said.

Witnesses said a pro-Islamist militia was behind the raid on the interior ministry unit, which opposes the election of Miitig, himself targeted in an attack hours earlier that caused no casualties.

The General National Congress, or interim parliament, passed a vote of confidence in a Miitig-led government, which critics have charged was "illegally elected" and imposed by Islamists.

The caretaker government said Wednesday it wanted a court to decide whether it should hand over power, and that it "commits itself to totally respecting all judicial decisions".

Thani said this was "not a dispute between the two governments, but an imbroglio within the GNC," which he urged to find a reasonable solution to the problem.

On Tuesday, gunmen attacked the family home of Miitig, who was elected to replace Thani, who resigned last month after what he said was an attack on him and his family.

- US: Leave immediately -

Amid the political and security turmoil in Libya three years after the NATO-backed revolution, the US State Department called on Americans to leave the country immediately.

"Due to security concerns, the Department of State has limited staffing at Embassy Tripoli and is only able to offer very limited emergency services to US citizens in Libya," a travel warning said.

"US citizens currently in Libya should exercise extreme caution and depart immediately."

The United States is deploying an amphibious assault ship with about 1,000 marines off the coast of Libya in case the embassy needs to be evacuated.

The precautions come amid persistent controversy over a September 2012 attack on the US consulate in Benghazi in which Ambassador Chris Stevens and three other Americans were killed.

Since Kadhafi's death, Libya has been dogged by power struggles among rival former rebel militias and is awash with arms.

Successive governments have failed to control the myriad militias that have carved out fiefdoms across the country, and Miitig is Libya's fifth post-Kadhafi premier.

He is due to lead a transition until fresh parliamentary elections are held on June 25.

Amid the dispute over Miitig, Haftar is garnering support from powerful military units and influential political figures for his offensive against jihadists.

The GNC has accused Haftar of launching a coup but he said the people had given him a "mandate" to crush jihadists after thousands rallied in his support in Benghazi and Tripoli last Friday.