At least three people have died as rival armed Libyan groups battle for control of Tripoli's international airport, according to a security official.
The week-long fight over the capital's airport is being waged by a powerful group from the western city of Zintan, which controls the facility, and Islamist-led groups, including fighters from Misrata, east of Tripoli.
The clashes resumed early on Sunday after ceasefire efforts failed.
An unnamed security official said two fighters from Misrata and a civilian died when a stray rocket hit his house.
A mortar shell struck a Libyan Arab Airlines plane and a column of black smoke could be seen rising from inside the airport, which has been closed since Monday.
Tripoli is witnessing one of its worst spells of violence since the toppling of longtime ruler Muammar Gaddafi in 2011.
The rival groups, made up largely of former rebels, have forced a weeklong closure of petrol stations and government offices.
In recent days, armed men have attacked vehicles carrying money from the Central Bank to local banks, forcing their closure.
The Central Bank had said banks would reopen on Sunday but they remained closed as the fighting resumed.
Khalifa Haftar, a renegade former general who is waging his own offensive against fighters in the eastern city of Benghazi, denounced what he called an attempt by "remnants and agents of terrorism'' to destroy Tripoli's airport and terrorise the people.
Haftar, who appeared on Libyan television on Saturday, said "our troops in Tripoli have bravely confronted the aggressive militia attacks" and vowed that the "coming few days will be decisive with the escalation of our military operations".
In Benghazi, Libya's second-largest city, armed men killed an army officer late on Saturday while he was driving home in his car, and early on Sunday a former special forces officer was shot dead in the Salmani business district, a security official said.
The UN Support Mission in Libya said last week it was temporarily withdrawing its staff because of the deteriorating security situation.