An image grab taken from the video shows Islamic State fighters with the handcuffed hostages. (Photo: Agence France-Presse)
Libya's air force chief said on Monday that at least 50 people had been killed in airstrikes by Egyptian and Libyan warplanes launched after jihadists 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 Islamic State 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 jihadists 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 jihadists.
"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 Muammar Gaddafi 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.