Fierce fighting between Islamists and a rogue Libyan general killed at least 18 people in Benghazi on Monday, triggering fears of an all-out war as hospitals urged citizens to donate blood.
Officials at hospitals in the eastern city, the birthplace of the 2011 NATO-backed uprising that toppled dictator Moammar Gadhafi, said at least 11 soldiers were among the dead and that 81 people were wounded.
The government of outgoing prime minister Abdullah al-Thani said it was holding an "emergency meeting" on the violence, which residents said had eased in the afternoon.
Also in Tripoli, gunmen opened fire on the road convoy of regular army chief Abdessalam Jadallah al-Abidi, without causing casualties, his spokesman said.
Col. Ali al-Shikhi said the soldiers guarding Abidi, who has criticized the actions in Benghazi of rogue general Khalifa Haftar, 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 was the bloodiest since 76 people were killed in mid-May when Haftar unleashed an offensive dubbed "Operation Dignity" to purge Libya of Islamists he brands "terrorists".
It 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 Center, Dr. Leila Buigiguis, said in remarks broadcast on television.
The education ministry closed schools, forcing the postponement of scheduled final exams.
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 neighborhood of Sidi Freij, a stronghold of Ansar al-Sharia.
Haftar spokesman Mohamed al-Hijazi called on residents in combat zones across Benghazi to evacuate.
Col. 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.
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."
Since the 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.