Warplanes have launched three air strikes on the Libyan city of Derna, a witness said, days after Egypt attacked camps there, saying it was targetting fighters 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 said one attack hit the western entrance to Derna and the other two hit Dahr al-Hamar in the south.

READ MORE: Egypt launches strikes in Libya after Minya attack

Egyptian jets attacked Derna on Friday, just hours after masked men boarded vehicles en route to a monastery in the southern Egyptian province of Minya and opened fire at close range, killing 29 and wounding 24.

Islamic State of Iraq and the Levant (ISIL, also known as ISIS) claimed responsibility for that attack in Egypt, the latest targetting Christian minority there - two church bombings also claimed by ISIL killed more than 45 last month.

Egypt, which attacked Derna again on Saturday, has carried out a number of air strikes on its neighbour since Libya descended into factional fighting in the years following the 2011 civil war that ousted Muammar Gaddafi.

Several armed groups, including ISIL, have gained ground in the chaos.

Egypt has been backing eastern commander Khalifa Haftar, whose Libyan National Army has been fighting armed goups in Benghazi and Derna for more than two years.

Speaking to Al Jazeera from Boston, Tarek Masoud of Harvard University said Egypt cannot solve its security problem by striking Libya.

"Are the people who perpetrated the latest attack in Egypt based in Libya?" he said.

"I don't know. But the fact that this happened so deep within Egypt suggests to me that the bases of operations of these kinds of attacks are not over the border in Libya, but are actually within Egypt.

"That of course means this is a much bigger problem, one that may not be solved by striking some terrorist bases in faraway Libya."

READ MORE: What's happening in Libya today?

Libyan National Army spokesman Colonel Ahmad Messmari told reporters in Benghazi late on Sunday that Haftar's forces were coordinating with Egypt's military in air strikes and the weekend raids targeted ammunition stores and operations camps.

Egyptian President Abdel Fattah el-Sisi said on Friday the air raids targeted fighters responsible for plotting the attack, and that Egypt would not hesitate to carry out additional strikes inside and outside the country.