East Libyan forces said they participated on Friday in air strikes launched by Egypt on the Libyan city of Derna, following a deadly attack on Christians in central Egypt earlier in the day, Reuters reported.
The East Libyan air force's media office said in a statement that the strikes had targeted forces linked to al-Qaeda at a number of sites, and would be followed by a ground operation.
A resident in Derna told Reuters they had heard four powerful explosions, and that the strikes had targeted camps around Derna used by fighters belonging to the Majlis al-Shura militant group.
Derna is one of the cities where east Libyan forces led by Khalifa Haftar, a close ally of Egypt, has been trying to gain control from Islamists and other opponents.
Haftar's forces have besieged the city and launched occasional air strikes.
Derna has a history of Islamist militancy and is where Islamic State set up its first presence in Libya in 2014. However, the jihadist group was later chased from the city by local fighters and rival Islamists from the Majlis al-Shura group.