CAIRO/BAYDA - Cairo carried out air strikes against Islamic State group targets in Libya on Monday after the militants posted a video showing the beheadings of 21 Egyptian Christians.

Egypt said a “tough intervention” was needed and with France called on the UN Security Council to “take new measures” against the militants in neighbouring Libya.

With Monday’s air strikes, Egypt opened a new front against the militants, who it is already battling in the Sinai Peninsula where scores of troops have been killed since the army toppled Islamist president Mohamed Morsi in July 2013. President Abdel Fattah al-Sisi, the former army chief who overthrew Morsi and has been criticised for a deadly crackdown on dissent, has presented Egypt as a key partner in international efforts against the militants.

Monday’s early morning air strikes hit IS camps and stores of weapons, the military said, hours after militants released gruesome footage of the beheadings that provoked outrage in Egypt.

Witnesses told AFP there were at least seven air strikes in Derna in the east, a hotbed of militancy since Libyan dictator Moamer Kadhafi was overthrown in 2011. It was not immediately clear whether other areas were also hit.

“Your armed forces on Monday carried out focused air strikes in Libya against Daesh camps, places of gathering and training, and weapons depots,” the military said in a statement, using the Arabic acronym for IS. It was the first time Egypt announced military action against Islamist targets in its western neighbour, having previously denied it targeted militants there.

Egypt has reportedly allowed the United Arab Emirates to previously use its bases to bomb militants in Libya. State television showed footage of Egyptian fighter jets it said were taking off to conduct the strikes. “Avenging Egyptian blood and retaliating against criminals and killers is a duty we must carry out,” the military said. The air strikes came hours after Sisi threatened a “suitable response” to the killings of the Coptic Christians.

Foreign Minister Sameh Shoukry was headed to Washington to take part in an “anti-terrorism” summit, the ministry said, calling for strong international action. “Leaving matters as they are in Libya without tough intervention to curb these terrorist organisations represents a clear threat to international security and peace,” it said. The brutal deaths of the Christians, who like thousands of poor Egyptians had travelled abroad to seek work, shocked their compatriots.

“Revenge is on the way”, read the banner on the front page of the official Al-Akhbar newspaper and both the Coptic Church and the prestigious Islamic Al-Azhar institution condemned the attack. In the village of Al-Our in Upper Egypt, where 14 of the victims were from, devastated family members gathered in the small local church. “My son travelled to Libya 40 days ago, he wanted to make money for his marriage,” said Boshra, whose 22-year-old son Kirolos was among the dead.

The White House led condemnation of the beheadings, saying the killers were “despicable”.

French President Francois Hollande agreed with Sisi that “the Security Council meet and that the international community take new measures to face up to this danger,” a statement from Hollande’s office said.

France is poised to sign a deal selling Egypt advanced Rafale fighter jets on Monday.

Meanwhile, Libya’s internationally recognised prime minister called for the West to launch air strikes to defeat Islamist militants who control Tripoli and have driven his government out of the capital.

Speaking hours before Egypt bombed Islamic State targets in Libya in retaliation after militants said they had beheaded 21 Egyptian Christians, Prime Minister Abdullah al-Thinni made a plea for Western military intervention in a country rapidly slipping into chaos.

“We have absolutely confirmed information that al Qaeda and IS are in Tripoli and....near Ben Jawad,” he said, referring to a central town controlled by a faction that supports a rival government.

“I ask world powers stand by Libya and launch military strikes against these groups,” he said. “This threat will move to European countries, especially Italy.”

Thinni, the internationally recognised premier, has been based in the east of the country since an armed group called Libya Dawn seized the capital in August. Libyan Dawn includes Islamists but denies that it has links to al Qaeda or to fighters that have sworn allegiance to Islamic State.

The North African country is in chaos as two rival governments and parliaments allied to separate armed factions fight for territory, four years after NATO war planes helped topple dictator Muammar Gaddafi.

Egypt’s military, joined by jets from Libya’s own air forces, bombed Islamic State targets inside Libya on Monday, a day after fighters proclaiming allegiance to the group released a video showing what they described as the beheading of 21 Egyptians captured in Libya.

A Libyan air force commander said 40-50 militants were killed in the Libyan-Egyptian strikes.

Egypt is worried about the rise of Islamic State, especially in areas near its border. It called on Monday for the US-led coalition that has been bombing Islamic State in Syria and Iraq to confront the group in Libya as well.

With Libya divided by two governments, the United Nations has been mediating to avert full-blown civil war. But little progress has been made in talks as the country is dominated by former rebels who helped oust Gaddafi but now fight each other.

“Dialogue is the only way to save Libya,” Thinni said in an interview at his government headquarters in Bayda, a town some 1,200 km to the east of Tripoli.

He insisted that talks need to be based on the assumption that one of two rival parliaments, the House of Representatives elected in June and also based in the east, is the legitimate assembly.

The UN has sought to widen its dialogue by including the previous parliament, known as General National Congress (GNC), which was reinstated in Tripoli by Libya Dawn.

“The redline, what we cannot give up, is the legitimacy of the elected House of Representatives,” Thinni said.

He warned that a military confrontation was still on option for his government. The air force of autonomous general Khalifa Haftar allied to Thinni has bombed targets in western Libya.

“We hope the dialogue is the way out... but if the dialogue fails, God forbid, then there is another opinion, the use of military force,” he said.