Egyptian jets bombed Islamic State targets in Libya on Monday, a day after the group there released a video showing the beheading of 21 Egyptian Christians, drawing Cairo directly into the conflict across its border.
Egypt said the dawn strike hit militant camps, training sites and weapons storage areas in neighbouring Libya, where civil conflict has plunged the country into near anarchy and created havens for armed factions.
While Cairo is believed to have provided clandestine support to a Libyan general fighting a rogue government in Tripoli, the mass killings pushed President Abdel Fattah al-Sisi into open action, expanding his battle against Islamist militancy.
Libya's air force also participated in Monday's attack on Derna — an eastern coastal city seen as a base for Islamic State fighters in the oil-rich nation.
"There are casualties among individuals, ammunition and the (Islamic State) communication centres," Libyan air force commander Saqer al-Joroushi told Egyptian state television, adding that between 40 to 50 militants were killed.
It was not possible to confirm those numbers.
"More air strikes will be carried out today and tomorrow in coordination with Egypt," said Joroushi, who is loyal to Libya's internationally recognised government, which has set up camp in the eastern city of Tobruk after losing control of Tripoli.
The rival Tripoli-based parliament, which is supported by some Islamist groups, condemned Monday's strike as an assault on the country's sovereignty.
Cairo also called on the U.S.-led coalition fighting Islamic State in Iraq and Syria to broaden the scope of their operations to include Libya, highlighting how the militant group is expanding its reach around the Arab world.
Since the fall of Libyan leader Muammar Gaddafi in 2011, a number of Islamist movements have taken hold. Recently, some have declared ties to Islamic State and claimed high-profile attacks in what appears to be intensifying campaign.
Last month, Islamic State claimed responsibility for an attack on the Corinthia Hotel in Tripoli, killing nine people, including an American security contractor and a Frenchman.
CHRISTIAN CONDEMNATION
Egypt is not the only Arab nation sucked into confrontation with Islamic State by the gruesome killings of its citizens.
Jordan has taken a leading role in conducting air strikes against the group in Syria and Iraq this month after the militants released a video showing a captured Jordanian pilot being burned alive in a cage.
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." Afterwards, he says: "And we will conquer Rome, by the will of Allah."
The head of the Roman Catholic Church, Pope Francis, condemned the killings. "They were killed simply for the fact that they were Christians," he said at the Vatican. "It makes no difference whether they be Catholics, Orthodox, Copts or Protestants. They are Christians!"
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.
"It's swift and decisive, it's not about strategy, it's about containing anger within Egypt," said Hassan Hassan, co-author of a book on Islamic State.
"Just like in Jordan, it's more about saving face, saying: 'You can't mess with us'. …. It's likely to evolve into a sustained strategy of helping in the fight against ISIS (Islamic State) in neighbouring countries."
Sisi sees radical groups in Libya as a major threat to Egypt's security. Fears the crisis there 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.
Italy also called for a U.N. response.
"In Libya, the situation is difficult but if it wants to, the international community has all the instruments necessary to be able to intervene," said Italian Prime Minister Matteo Renzi after talking by telephone to Sisi.
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.
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 Sisi toppled Mursi and launched a crackdown which killed hundreds of Islamists and jailed thousands of others
