It was the first time Egypt confirmed launching air strikes against the group in neighboring Libya, showing President Abdel Fattah al-Sisi is ready to expand his fight against Islamist militancy beyond Egypt’s borders.
Egypt said the dawn strike, in which Libya’s air force also participated, hit Islamic State camps, training sites and weapons storage areas in Libya, where civil conflict has plunged the country into near anarchy and created havens for militia.
A Libyan air force commander said between 40 to 50 militants were killed in the attack. “There are casualties among individuals, ammunition and the (Islamic State) communication centers,” Saqer al-Joroushi told Egyptian state television.
“More air strikes will be carried out today and tomorrow in coordination with Egypt,” he said.
The 21 Egyptian Coptic Christians, who had gone to Libya in search of work, were marched to a beach, forced to kneel and then beheaded on video, which was broadcast via a website that supports Islamic State.
Before the killings, one of the militants stood with a knife in his hand and said: “Safety for you crusaders is something you can only wish for.”
Egypt’s Coptic Christian pope was one of the public figures who backed Sisi when he, as army chief, ousted Islamist president Mohamed Mursi in 2013 after mass protests against him.
The beheadings could pile pressure on Sisi to show he is in control of Egypt’s security, even though he has already made progress against Islamist militant insurgents in the Sinai.
Egypt has been trying to project an image of stability ahead of an investment conference in the Red Sea resort city of Sharm el-Sheikh in March designed to lure billions of dollars into an economy battered by turmoil since the 2011 uprising.
“This allows Sisi to come up looking very strong, showing Egyptians that Egypt is projecting power in the region. It helps sort of mitigate other issues,” said Kamran Bokhari, a Middle East analyst at Stratfor.
“He may not be looking strong on the economic front or domestic security front, and there’s the question of political legitimacy that still hangs there, but he is saying that Egypt will become like Libya without him.”
Sisi, who has called for a global effort to eradicate militancy, which he says is harming Islam, sees radical groups in Libya as a major threat to Egypt’s security.
Fears that the crisis could spill across the border have prompted Egypt to upgrade its military hardware.
France has said Egypt will order 24 Rafale fighter jets, a naval frigate and other equipment in a deal to be signed in Cairo on Monday worth more than 5 billion euros ($5.7 billion).
French President Francois Hollande said on Monday that he and Sisi wanted the United Nations Security Council to discuss Libya and take new measures against the Islamic State, whose influence has spread rapidly from its original Syrian base.
Egypt, the Arab world’s most populous nation, has not taken part directly in the U.S.-led air strikes against Islamic State strongholds in Iraq and Syria, focusing instead on the increasingly complex insurgency at home.
The United Arab Emirates, a close ally of Sisi, said it “would put all its capabilities to support … Egypt’s efforts to eradicate terrorism and the violence against its citizens”, according to the UAE foreign minister who was cited on the WAM state news agency.
A number of Arab states are now directly attacking Islamic State, with Egypt following on the heels of Jordan, which has launched repeated airstrikes against militants in Syria this month following the killing of a Jordanian pilot.
The Libyan air force commander, Joroushi, said Egyptian and Libyan planes had combined to strike targets in the eastern town of Derna. Libyan war planes then attacked the central cities of Sirte and Ben Jawad, he told Reuters.
Security officials say militants in Libya have established ties with Sinai Province, a group operating from Egypt’s vast Sinai Peninsula that has pledged allegiance to Islamic State.
Sinai Province has killed hundreds of Egyptian soldiers and police since the army toppled Mursi.
The upheavals in Egypt have pummeled the local economy and thousands of Egyptians desperate for work have traveled to oil-rich Libya, despite the government’s advice not to go to a state sliding into chaos.
A number of Islamist militant groups have been active in Libya since the fall of Muammar Gaddafi in 2011 left the country without a strong central government. A few have declared ties to Islamic State and claimed high-profile attacks over recent weeks in what appears to be an intensifying campaign.