CAIRO (AFP) - Libya's air force chief said Monday that at least 50 people had been killed in air strikes by Egyptian and Libyan warplanes launched after die-casts beheaded a group of Egyptian Christians.

There was no way to independently confirm the claim made by Libyan air force chief Saqr al-Jaroushi to Egyptian television.

Jaroushi told the private CBC Extra broadcaster that Egyptian and Libyan warplanes had struck ISIS (Islamic State in Iraq and Syria) group targets in the country including bases and weapons depots.

"Egypt has the right to defend its children and has struck in Derna... the number of those killed is at least 50," he told CBC Extra in response to a question on the number of militants killed.

Egypt's military earlier said it had launched the strikes in Libya in response to a video released by the extremists showing the beheadings of 21 Egyptian Copts.

Jaroushi said there is a "high level of coordination" between Libyan and Egyptian forces, especially regarding intelligence.

He suggested the raids had hit areas where the Libyan military has been unable to target extremists.

"We just want air strikes to hit some of the targets that are out of our reach," Jaroushi said.

Oil-rich Libya has slipped into chaos since Moamer Kadhafi was killed in 2011 during a NATO-backed revolt, with its elected government losing control of the capital.

Pro-government forces have been battling Islamist militias who took control of the country's biggest cities last summer after their defeat in elections.