Egyptian President Abdel Fattah Al-Sisi called for a United Nations resolution mandating an international coalition to intervene in Libya after its jets bombed Islamic State of Iraq and Syria (ISIS) targets there.

"There is no other choice, taking into account the agreement of the Libyan people and government and that they call on us to act," he told France's Europe 1 radio in an interview aired on Tuesday.

Asked if it would recommence its own action: "We need to do it again, and all of us together."

ISIS released a video on Sunday showing the beheading of 21 Egyptian Christians, drawing Cairo directly into the conflict across its border and raising concerns the Islamist insurgents, already active in Syria and Iraq, were spreading their influence further.

Referring to the 2011 Libyan war in which France was part of an international coalition backing forces that deposed former leader Moammar Gadhafi, Sisi called it an "unfinished mission."

"We abandoned the Libyan people as prisoners to extremist militias," he said.

In Rome, Italian Prime Minister Matteo Renzi also called for action from the United Nations, but did not say whether Italy itself would support any direct military operation in Libya.

"There was renewed Italian commitment for strong diplomatic action within the framework of the UN and support for an urgent initiative at the Security Council to promote stability and peace in Libya," said a statement following a meeting between Renzi and his defence and interior ministers.

Libya is separated from the Italian island of Sicily by only a few hundred kilometres of sea and has been a launching pad in recent years for hundreds of thousands of African and Middle East migrants seeking a better life in Europe.

Foreign Minister Paolo Gentiloni and Defence Minister Roberta Pinotti have both said Rome would be ready to join any military intervention but Renzi has struck a more cautious note, saying on Monday it was important to avoid "hysteria" and that any action had to be under UN authority.

Sisi called on militias to hand in their arms but urged weapons to be supplied to Libya's internationally recognized government, based in the eastern city of Tobruk after rivals seized power in Tripoli.

The Tobruk government has already asked for the lifting of an international arms embargo to help it take back control of the country.