Warplanes continue pounding Libya's Derna days after Egyptian intervention

Warplanes launched three airstrikes on the Libyan city of Derna on Monday, according to witnesses, days after Egypt attacked camps there, claiming it was targeting militants responsible for killing Egyptian Christians.

There was no immediate confirmation of Monday's strikes from officials in Libya or neighbouring Egypt, nor any claim of responsibility for the raid on the city at the eastern end of Libya's Mediterranean coast.

The witness told Reuters that one attack hit the western entrance to Derna and the other two hit Dahr al-Hamar in the south.

On Friday, Egypt's air force launched air raids on Derna, only hours after masked gunmen attacked a bus carrying Coptic Christians south of Cairo, killing 30 people and wounding at least 24 others.

The Islamic State group on Saturday claimed responsibility for the attack, the latest in a series of IS strikes that have killed more than 100 Copts in Egypt since December.

Egypt's foreign ministry said it had delivered a letter on Saturday to the United Nations Security Council informing it that the strikes were conducted as an act of "legitimate self-defence", according to a ministry statement.

Cairo claims it has proof that militant fighters based in Derna carried out the massacre in Minya.

On Saturday, al-Qaeda affiliate Mujahideen Shura Council in Derna (MSCD) denied involvement in the deadly attack on Egypt's Copts.

The militant group claimed it does not target unarmed civilians in Libya or Egypt, adding said Cairo's airstrikes were "a diversion to the Egyptian Public from [President] Sisi's failure to address the security and economic crises" in the country.

Egypt has carried out a number of airstrikes on its neighbour since Libya descended into factional fighting in the years following the 2011 civil war that ousted Muammar Gaddafi.

Islamist militant groups, including Islamic State, have gained ground in the chaos.

Egypt has been backing eastern commander Khalifa Haftar, whose Libyan National Army has been fighting Islamist militant groups and other fighters in Benghazi and Derna for more than two years.

Haftar's forces carried out a "joint operation" with Egypt in Derna on Friday, the air force said in a statement carried by the LANA news agency loyal to Libya's eastern administration.