Libya's new government announced Monday it had taken office, despite the refusal of Abdullah al-Thani's cabinet to leave power, as violence intensified in the east of the country following the launch of a deadly "anti-terrorist" campaign.
Prime Minister Ahmed Miitig, 42, said in a statement he had convened his ministers for the first time since his disputed election in May, amid an ongoing power struggle in Tripoli.
His spokesman said Miitig had "no difficulties" in accessing the parliamentary building.
"There was no opposition from the security services deployed in front of the building," said the spokesman.
Miitig is Libya's fifth prime minister since dictator Moamer Kadhafi was toppled and killed in a 2011 uprising.
The General National Congress elected Islamist-backed businessman Miitig in a chaotic vote in early May, days after gunmen stormed the GNC to interrupt an earlier ballot.
However some political opponents refused to recognise the new leader.
Miitig is due to lead a short transitional period until legislative elections are held on June 25, and the new parliament will replace the GNC and form another cabinet.
Fierce fighting between Islamists and a rogue general's forces in the eastern city of Benghazi meanwhile killed 21 people earlier Monday.
Hospital officials in the port city, the birthplace of the 2011 NATO-backed uprising that toppled dictator Moamer Kadhafi, said at least 11 soldiers were among the dead and 112 people wounded.
The government of outgoing prime minister Thani said it was holding an "emergency meeting" on the violence, which residents said eased in the afternoon.
It was the deadliest violence since 76 people were killed in mid-May as rogue general Khalifa Haftar unleashed an offensive dubbed "Operation Dignity" to purge Libya of Islamists he brands "terrorists".
Underscoring the mounting chaos in the North African country, gunmen on Monday opened fire on the road convoy of army chief Abdessalam Jadallah al-Abidi in Tripoli, without causing casualties, his spokesman said.
Colonel Ali al-Shikhi said the guards of Abidi, who has criticised Haftar's actions in Benghazi, returned fire.
An air force commander said the clashes in Benghazi erupted when three Islamist groups, including Ansar al-Sharia, attacked a base of elite forces who support Haftar.
Images posted on the Internet showed army assault helicopters firing missiles at suspected Islamist targets.
The fighting triggered by Haftar's operation has triggered panic in Benghazi, Libya's second city where hospitals appealed to people to donate blood.
"Benghazi is suffering, people are fed up, spare them," the head of the Benghazi Medical Centre, Doctor Leila Buigiguis, said in remarks broadcast on television.
The education ministry closed schools, forcing the postponement of scheduled final exams.
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Residents cowered indoors and many shops and businesses were closed as gunfire rang out and explosions shook Benghazi, witnesses said.
They said some families were trapped in the western neighbourhood of Sidi Freij, a stronghold of Ansar al-Sharia.
Haftar spokesman Mohamed al-Hijazi called on residents in combat zones across Benghazi to evacuate.
Colonel Saad al-Werfelli, who commands the Benghazi air force base, said the jihadists "bombarded base 21 early on Monday, killing and wounding soldiers (from the elite unit) who were trapped inside".
The air force retaliated by launching strikes on the assailants, added Werfelli, who along with the elite forces backs Haftar's campaign against Islamists accused of repeated violence in Benghazi.
- 'Enemy of Islam' -
The latest bloodshed comes a day after Haftar's forces launched fresh air raids on Islamists in Benghazi, with one strike targeting a meeting of Ansar al-Sharia, one of his aides said.
Al-Qaeda in the Islamic Maghreb has urged Libyans to fight Haftar and his so-called National Army, labelling the ex-army general an "enemy of Islam".
Authorities have denounced Haftar as an outlaw, but after thousands of Libya rallied for his support he said he has a mandate from the people to pursue his offensive to crush "terrorism".
Since 2011, Libya has been rocked by lawlessness with near-daily attacks blamed on radical Islamists targeting security forces in Benghazi.
The interim authorities, caught in their own power struggle, have been unable to stamp out the violence in the absence of a strong army and police force.
Ansar al-Sharia, classified as a terrorist group by the United States, was backed by the February 17 Brigades of ex-rebel leader Rafallah al-Sahati and the Libya Shield Force Islamist groups, said Werfelli.
The powerful February 17 group of ex-rebels denied any involvement in Monday's fighting, in a statement posted on Facebook.
The group of ex-rebels is suspected of having strong ties with Ansar al-Sharia, which has threatened Haftar that he could end up like Kadhafi, killed by rebels eight months after the 2011 uprising.
Haftar, 71, lived in exile in the United States before returning home to command ground forces in the uprising.
Last week, he said in a statement read on a private television that he would not rest until he has purged Libya of Islamists.
"No steps backwards until the country is liberated, security and stability restored and freedom and democracy established," he said.
But many in Libya doubt that he will have any impact on the Islamists and question his motivation.