Two unidentified aircraft roared over Libya's capital before dawn on Monday as loud explosions were heard, days after new clashes between militias prompted hundreds of people to flee.
A statement by the provisional government, which lacks any real authority, said it was not known whose aircraft had attacked militia positions.
However, an aide to rogue general Khalifa Haftar, who has launched an offensive against Islamists in second city Benghazi, said the aircraft had been sent by him.
Saqr Jarouchi, also a dissident general, later told AFP: "Those were our planes that launched raids."
But an air force unit that has refused to join Haftar's offensive in the eastern city of Benghazi dismissed the claim, saying the aircraft were "foreign, not Libyan".
The group said in a statement Libyan aircraft are not equipped to make night flights and cannot be refuelled in flight, particularly if they take off from remote air bases controlled by Haftar's forces.
The mystery aircraft first flew over at around 2:00 am (0000 GMT) and a resident told AFP he heard a loud explosion which was followed by others.
"The explosions were clearly heard in eastern districts of Tripoli, 15 kilometres (10 miles) from the town centre," he said.
Television channel Libya Awalan (Libya First), which is close to Haftar, said: "Military planes bombarded various positions" near Tripoli. It gave no further details.
Haftar's aide said the attacks targeted the Islamist-linked militia of Misrata which has been battling nationalist fighters from Zintan for control of Tripoli international airport.
- 'Stop fighting' -
The airport, closed since July 13, is in the hands of militiamen from Zintan, southwest of Tripoli.
They have been fending off a challenge from the fighters from Misrata, east of the capital, for control of a bridge giving access to the airport.
Haftar in May launched an offensive dubbed "Operation Dignity" against radical Islamist groups which have held sway in Benghazi since the fall of long-time dictator Moamer Kadhafi in 2011.
Monday's government statement said an inquiry had been launched into the attack by the mystery planes.
"These parties must stop fighting, agree to talk and withdraw from Tripoli and other Libyan towns," the statement said, adding that the government had been in contact with "friendly" states to try to identify the aircraft.
The United States denied social media rumours of US involvement.
"The United States was not involved whatsoever in these events," State Department deputy spokeswoman Marie Harf said.
"We continue to seek more information and cannot confirm any details at this time about who took these airstrikes," she added.
France also denied rumours of French involvement in air strikes.
"Rumours of air raids in Libya in which France was involved are wrong," the foreign ministry spokesman said in Paris.
"France's priority is a political deal that will end fighting in Tripoli, Benghazi and everywhere in Libya."
New skirmishes between the rival militias raged in Tripoli on Friday and Saturday, with Grad missiles and artillery used but there were no immediate reports of casualties.
State news agency Lana said around 1,000 families had fled the fighting.
The clashes quietened on Sunday when the Misrata brigade claimed to have taken a bridge and an army base, although the claim was impossible to confirm independently.
Libya's newly elected parliament, meeting in the eastern city of Tobruk to avoid the Tripoli violence, called last Wednesday for foreign intervention to protect civilians.
Since launching his offensive in May, Hafter has rallied support from the public and members of the security forces, but other forces have resisted him and authorities regard him as an outlaw.