The airstrikes bring Egypt overtly into Libya’s turmoil, showing Cairo’s alarm over the growing stronghold of radicals on its western border as it also fights a militant insurgency of ISIS allies on its eastern flank in the Sinai Peninsula.

Libya is where the extremist group has built up its strongest presence outside Syria and Iraq, and the government of President Abdel-Fattah al-Sisi is lobbying in Europe and the United States for a coordinated international response similar to the coalition air campaign in those countries.

“Leaving things in Libya as they are without decisive intervention to suppress these terror groups constitutes a clear danger to international peace and security,” Egypt’s Foreign Ministry said.

Egypt launched U.S.-made F-16 fighter jets from bases near its border several hours apart and struck targets in the eastern Libyan city of Darna, according to Egyptian and Libyan security officials, who spoke on condition of anonymity because they were not authorized to talk the press.

Egypt’s military announced the first round of strikes on state radio – the first public acknowledgement of military action in post-Moammar Gadhafi Libya. The military’s statement said weapons caches and training camps were destroyed “to avenge the bloodshed and to seek retribution from the killers.”

“Let those far and near know that Egyptians have a shield to protect and safeguard the security of the country and a sword that cuts off terrorism,” it said.

Libyan air force chief Saqr al-Jaroushi told a private Egyptian broadcaster that at least 50 people were killed, a toll which could not be confirmed, and that Libyan warplanes also targeted the jihadis.

The strikes came hours after ISIS issued a grisly video of the beheadings of 21 Egyptian Christians.

U.N. chief Ban Ki-moon denounced the killings and the Security Council said the murder of the Egyptian Christians was a “heinous and cowardly” act.

With almost no state control in much of Libya, extremists loyal to ISIS have seized control of Darna and the central city of Sirte and have built up a powerful presence in the capital Tripoli and second city Benghazi.

Without publicly acknowledging it, Egypt and the United Arab Emirates carried out airstrikes against Islamist-allied militias last year, according to U.S. officials. Egypt and the Gulf are backing Libya’s internationally recognized government, which was driven into the far east of Libya after Islamist militias took control of the capital, Tripoli.

The Foreign Ministry in Cairo called Monday for political and material support from the U.S.-led coalition staging airstrikes against ISIS in Iraq and Syria. But Egyptian security officials said Cairo does not want to be drawn into a ground war, and for now, wants foreign military intervention restricted to airstrikes.In support of this campaign, they said, Egypt has been amassing intelligence on extremists in Libya in a joint effort with the Libyan armed forces and West European nations, including France.

“We will not fight there on the ground on behalf of anyone, but we will not allow the danger to come any closer to us,” said one Egyptian official, who claimed that intelligence recently gathered in Libya suggested advanced preparations by ISIS militants to cross the border into Egypt. He did not elaborate.

Egypt is already battling an Islamist insurgency in the strategic Sinai Peninsula, where militants recently declared their allegiance to ISIS. Those fighters rely heavily on arms smuggled from Libya, which has slid into chaos since the 2011 uprising that toppled Gadhafi’s 41-year rule.

Sisi spoke with France’s president and Italy’s prime minister Monday about Libya, and sent his foreign minister, Sameh Shoukri, to New York to consult with U.N. officials and Security Council members ahead of a terrorism conference opening Wednesday in Washington.

The idea of a wider intervention has gained traction with Italy, whose southern tip is less than 800 kilometers from the Libyan coast. One of the militants in the video of the beheaded Egyptians boasted the group plans to “conquer Rome.”