CAIRO — Egypt conducted an airstrike against an Islamist stronghold in Libya on Monday in retaliation for the beheading of at least a dozen Egyptian Christians by a local franchise of the Islamic State, in Cairo’s deepest reach yet into the chaos that has engulfed its neighbor.
Hinting at possible further action, President Abdel Fattah el-Sisi of Egypt said in a statement that he had convened “a continuous session” of his National Defense Council to monitor events in Libya and to weigh additional measures. But the strike itself, hitting in the Libyan town of Derna at dawn, was a new turn in the breakdown of regional order in the aftermath of the Arab Spring revolts and the Islamic State’s emergence.
Nearly three and a half years after the ouster of Col. Muammar el-Qaddafi, two rival coalitions of militias are battling for control over Libya and its vast resources, including nearly $100 billion in financial reserves, untapped oil deposits, and a long Mediterranean coast facing Europe. In the absence of any effective government or even a dominant force, a multifaceted proxy war has erupted as rival Arab states back competing militias and extremist groups like Al Qaeda and the Islamic State seek to expand their operations.
Mr. Sisi, a former general who led the ouster of Egypt’s Islamist president in 2013, has watched with growing concern as a coalition of moderate Islamists, extremists and regional militias seized control of the Libyan capital, Tripoli, last year and set up their own provisional government.
Together with the United Arab Emirates, Mr. Sisi has covertly backed a rival coalition that has coalesced around a Libyan general’s campaign to drive out the Islamist and regional militias. Last summer, Egypt provided bases for jets from the United Arab Emirates to launch at least two airstrikes against Islamist forces in Tripoli, Western officials have said, although neither country has publicly acknowledged its role.
Egypt’s strikes on Monday now threaten to drag it deeper into Libya’s messy internal conflict at a time when Cairo is already straining to revive a battered economy and suppress its own domestic Islamist insurgency — centered in the Sinai Peninsula but now also fighting under the banner of the Islamic State.
In this new theater, Egypt is highly vulnerable to potential counterattacks by Islamist forces, in part because of its long and porous desert border with Libya, but also because of the continued presence of large numbers of Egyptian citizens inside Libya. Egyptian workers often seek jobs in oil-rich Libya, and a spokesman for the Egyptian Foreign Ministry said Monday that “hundreds of thousands” remained inside the country.
For its part, the Islamic State may consider Egypt’s entry into the Libyan battle a strategic success, analysts said, in part because the extremists seek to capitalize on the spreading chaos.
“They want to stretch the Egyptian military because they are fighting in the Sinai, too,” said Aaron Y. Zelin, a researcher at the Washington Institute for Near East Policy who tracks the group. He argued that the extremists would rally local support against Egypt’s military interference — especially if its airstrikes hit civilians — but also that the Islamic State had built its ideology on cultivating such enemies.
“They see it as proof that God is on their side, that even as all these forces are arrayed against us, we are ‘remaining and expanding,’ as their saying goes,” he said. “This is red meat for their base of supporters.”
A similar dynamic unfolded this month when Jordan carried out days of bombing raids against the Islamic State in Syria in retaliation for its videotaped burning to death of a captured Jordanian pilot.
Egyptian militants, including the self-proclaimed Sinai Province of the Islamic State, have killed hundreds of soldiers and policemen in the 18 months since Mr. Sisi took power. They killed as many as three dozen Egyptians in one night of coordinated bombings at the end of January.
But the events that led to Egypt’s bombing on Monday began several weeks ago with the disappearance of about 20 Egyptian Christians working in the mid-coastal Libyan city of Surt.
Fighters identifying themselves as the Tripolitania Province of the Islamic State — adopting the name of one of the three traditional provinces based on Ottoman-era divisions — released a photograph last month showing that they had captured the Egyptian “crusaders.”
Then on Sunday night, the media arm of the central Islamic State group released a video headlined “A Message Signed With Blood to the Nation of the Cross,” which appeared to show at least a dozen of those hostages being paraded along a rocky Mediterranean beach in western Libya.
All wore orange jumpsuits and were escorted by a row of masked fighters dressed in black with ceremonial knives at their chests — details identical to previous Islamic State videos. After a short speech delivered in fluent English by the lead executioner, the fighters forced their captives to the ground, sawed through their necks and let their blood darken the waves.
In a televised address later Sunday night, Mr. Sisi declared that “Egypt preserves the right to respond, in the appropriate manner and timing, to exact retribution.”
In state news media reports issued Monday around 8:30 a.m., the Egyptian military said its F-16 fighters had struck camps, training facilities and weapons depots belonging to the Islamic State in Libya. A statement from the military called the attack “a response to the criminal acts of terrorist elements and organizations inside and outside the country.”
“We stress that revenge for the blood of Egyptians, and retribution from the killers and criminals, is a right we must dutifully enforce,” the military said, and Egyptian state television showed footage of the F-16s taking off in the dark as the statement was read on the air.
The military statement did not disclose the location of the strikes. But a Foreign Ministry spokesman, Badr Abdelatty, later confirmed news reports that the jets had hit Derna, Libya, where some of the local Islamist fighters have declared themselves the Barqa Province of the Islamic State.
Although far from Tripolitania Province, where the Islamic State group that killed the Egyptian Christians is from, Derna is close enough to the border for Egypt’s jets to reach it easily without having to refuel en route. Western officials, speaking on the condition of anonymity, noted that none of the three Islamic State “provinces” were open or visible enough to easily target, suggesting that even a prolonged campaign of airstrikes might do little harm to the groups.
But the strikes drew applause from Libya’s internationally recognized government, which relocated from the capital around the time it was taken over by an Islamist-allied militia and now sits near the Egyptian border in a town under the protection of Gen. Khalifa Hifter, who is leading the fight against the Islamists.
“Egypt has helped us as we requested,” Col. Saqer al-Joroshi, a commander under General Hifter, said by telephone in an interview with an Egyptian television network. Mr. Joroshi estimated that the strikes had killed “not less than 40 or 50” people.
The Islamist-allied coalition, which calls itself Libya Dawn and has established a provisional government in Tripoli, sought to deny that the Islamic State executions had taken place, reinforcing criticisms that the coalition willingly collaborates with such violent extremists.
In a statement, the Libya Dawn government dismissed the execution video as “a Hollywood film” contrived by its opponents. It called Mr. Sisi a “terrorist criminal and murderer” and charged that the Egyptian airstrikes in Derna had killed civilians. (Mr. Joroshi said no civilians had been killed; his assertion could not be verified.)
In what was apparently a threat, the same statement also warned all Egyptians to leave Libya within 48 hours “to preserve their safety from any revenge attacks.”
Mr. Abdelatty, the Foreign Ministry spokesman, said Egypt had established an emergency consular services center to help Egyptians caught inside Libya get to safe havens or return to Egypt.
The United States and its allies have tried to draw the Libyan factions into negotiations to form a unity government and dissuade them from demanding the complete military defeat of their opponents before any such talks.
Western officials have previously argued that military escalations such as Egypt’s bombing on Monday pose obstacles to a negotiated, political solution, but some have also acknowledged Egypt’s right to respond to an attack on its civilians. A State Department representative declined to comment.
In a statement, Mr. Sisi said he had sent Egypt’s foreign minister to New York and Washington “to ensure that the international community lives up to its responsibilities,” because Libya had now become “a threat to international peace and security.”