Egyptian warplanes bombed sites in Libya early today, a day after Islamic State (Isis) militants released a video depicting the apparent mass beheading of 21 Egyptian hostages.
The air strikes targeted training locations and weapons stockpiles belonging to Isis in Libya, Egypt's military said in a statement released on its Facebook page.
The strikes took place, the statement said, "in response to criminal acts of terrorist elements and organisations inside and outside the country". All of the warplanes returned safely to base, according to the military.
The raids represent the first time Egypt has acknowledged direct military involvement since Libya's crisis began nearly four years ago with an armed uprising that toppled autocrat Muammar Gaddafi.
Libya's air force also launched strikes in the eastern city of Darna, which was taken over by an Isis affiliate last year. An air force commander said 40-50 militants were killed.
"There are casualties among the individuals, ammunition and the communication centres belonging to them," Saqer al-Joroushi said on Egyptian state television. "The number of deaths are not less than 40 or 50 for sure," he said.
François Hollande, the French president, said today that the UN security council should meet over the situation in Libya.
Egypt has provided clandestine support to forces allied to Libya's internationally recognised government, which fled the capital for the eastern cities of Bayda and Tobruk last year. According to western officials, Egypt also allowed its bases to be used for air strikes in Libya in 2014. Egyptian government officials denied such military involvement. Egypt and the United Arab Emirates are among the key supporters of Khalifa Heftar, a renegade Libyan general, now allied with the recognised government, leading a campaign against a rival Islamist-leaning government in Tripoli and its allied militias.
In the context of the chaotic civil war in Libya, armed groups claiming allegiance with Isis have claimed attacks in various sections of Libya. Libyan fighters have circulated to and from the war in Syria, and experts say Isis has sought alliances with local armed groups in Libya.
The video released on Sunday claims to show the killing of 21 Coptic Egyptian hostages on a beach in Libya. The online clip is shot in a similar style to previous videos published by Isis militants in the group's core in Iraq and Syria. The self-proclaimed Islamic State seized vast chunks of territory in those two countries.
The US said the video showed the "wanton killing of innocents" and the UK foreign minister condemned the "barbaric" act.
At least 21 Egyptians were kidnapped in two separate incidents in the city of Sirte, Libya in December and January. Relatives of the hostages had previously identified the captured men in media released by Isis, including an online magazine published days ago.
The video depicts several men in orange jumpsuits being led along a beach, each accompanied by a masked militant. The men are made to kneel and one militant, dressed differently to the others, addresses the camera in North American-accented English.
"All crusaders: safety for you will be only wishes, especially if you are fighting us all together. Therefore we will fight you all together," he says. "The sea you have hidden Sheikh Osama bin Laden's body in, we swear to Allah we will mix it with your blood."
The men are then made to lie face down and all are simultaneously beheaded. The militant speaker then points northward and says: "We will conquer Rome, by Allah's permission."
Mina Thabet, a researcher at the Egyptian Commission for Rights and Freedoms, who has been communicating regularly with the families of the hostages, said he believed that all but one of the victims in the video were Egyptian.
Thabet blamed the Egyptian government for what he asserted was a delayed response to the hostage crisis. "There is blood on the hands of the authorities who could have saved them but failed to."
On Sunday, the Egyptian president, Abdel Fatah al-Sisi, said on national television that Egypt reserved the right to respond to the murders in a way it sees fit. Sisi warned that Cairo would choose the "necessary means and timing to avenge the criminal killings".
The Coptic church called on its followers to have "confidence that their great nation won't rest without retribution for the evil criminals".
A pro-jihadi Facebook page published photos this morning showing a plume of smoke and damaged buildings in the eastern Libyan city of Derna, which it claimed were the result of the air strikes. The page, which could not be independently verified, said people had been killed in the strikes.