Egypt reported that its war planes had struck Isis targets in Libya, shortly after President Abdel Fatah al-Sisi vowed revenge for the release by Isis-affiliated militants of a video of a mass killing of Christians.
A spokesman for the Armed Forces General Command announced the strikes on state radio Monday, marking the first time Cairo had publicly acknowledged taking military action in neighbouring Libya.
The statement said the warplanes targeted weapons caches and training camps before returning safely. It said the strikes were “to avenge the bloodshed and to seek retribution from the killers”.
“Let those far and near know that Egyptians have a shield that protects them,” it said.
Libya’s air force meanwhile announced it had launched strikes in the eastern city of Darna, which was taken over by an Isis affiliate last year. The announcement, on the Facebook page of the air force chief of staff, did not provide further details.
The video, released on Sunday evening, claimed to show the mass beheading of 21 Christians – believed to be mostly Egyptians – kidnapped in Libya.
The US said the video showed the “wanton killing of innocents” and the UK foreign minister condemned the “barbaric” act.
The five-minute video was filmed in a style similar to that of previous videos depicting the murders of western prisoners by Isis, an armed group that overran large parts of Iraq and Syria last year.
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 Egyptians.
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.”
In the weeks between the abduction and the release of the video, the families of the kidnapped Egyptians criticised what they saw as an inadequate response to the kidnapping.
The men’s families complained that Egypt’s ministry of foreign affairs did not immediately respond to their inquiries. One relative said the ministry had advised the families not to speak to the media.
The Egyptian president, Abdel Fatah al-Sisi, called an urgent meeting of the national defence council and declared a seven-day mourning period, according to a statement from the president’s office.
“It is with deep sorrow that President Abdel Fatah al-Sisi mourns the Egyptian victims of an abhorrent act of terrorism in Libya and offers his deepest condolences to the Egyptian people for their grave loss,” the statement said.
He later 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 in a statement called on its followers to have “confidence that their great nation won’t rest without retribution for the evil criminals”.
In el-Aour, an impoverished village 125 miles south of Cairo that was home to 13 of the hostages, friends and family assumed the worst when the photo was published on Thursday.
On Saturday, the community showed its sorrow. Men covered their heads with dirt in a sign of both grief and shame. Women slapped their own faces or let out shrieks of pain.
Samuel Walham’s family said they immediately recognised him from the picture showing him kneeling on the beach alongside four other hostages each flanked by a knife-wielding militant.
“Look at my love. Look how beautiful he is,” Walham’s mother, Ibtassal Lami, said through tears as she cradled a photo of her son and women wailed in the family’s ramshackle, two-storey home. “He only went there to earn his living.”
Egypt announced on Friday an offer to facilitate the exit of Egyptians living in Libya. Tens of thousands of Egyptians live and work in the country.
The hostages had previously been identified as workers living in the city of Sirte. Several of the men were captured from a car leaving the city in late December. Others were seized from a house in Sirte in January, where survivors said the attackers separated Christians from Muslims, taking only the Christians as hostages. Fourteen of the men came from the village of Al-Our, in the province of Minya in central Egypt.
Militants have frequently attacked Egyptian citizens and installations in Libya over recent months of turmoil. In January 2014 five Egyptian embassy staff were kidnapped and later released.
Egypt’s embassy in Tripoli was also the target of a bombing last November. Egypt is a key backer of Libya’s internationally recognised government which has retreated to the eastern city of Tobruk.
Egyptian Coptic Christians have also been singled out for attacks. In 2012 and 2013, explosions have hit at least two Coptic churches. In 2014, a reported 14 Egyptian Copts were killed, including a physician, his wife and daughter who were killed in Sirte in December.
The video was released the day after Isis took control of Sirte, birthplace of the late dictator Muammar Gaddafi, with gunmen capturing government buildings and radio stations, the third town in Libya it now holds.
Sirte had been held by Libya Dawn, an Islamist-led militia coalition that rebelled against the elected government in the summer and has been fighting a bitter war with government forces ever since.
Isis has emerged in recent weeks as a third side in a civil war, raising western fears that it will launch terror strikes across the Mediterranean against Europe. Fears of an attack by Isisprompted Italy to evacuate its Tripoli embassy on Sunday, the last major power to do so.
The British foreign secretary, Philip Hammond, condemned the murders and said the UK remains fully supportive of the UN’s efforts to build a national unity government for Libya.
“Such barbaric acts strengthen our determination to work with our partners to counter the expanding terrorist threat to Libya and the region,” he said.
“Acts of terrorism should not be allowed to undermine Libya’s political transition. We remain fully supportive of the UN’s efforts to build a national unity government for Libya and to bring a political solution to the ongoing security crisis. Those who support terrorists can have no part in this process.”
The White House called the killings “despicable and cowardly”.
“This wanton killing of innocents is just the most recent of the many vicious acts perpetrated by Isil-affiliated terrorists against the people of the region, including the murders of dozens of Egyptian soldiers in the Sinai, which only further galvanises the international community to unite against Isil,” said spokesman Josh Earnest.
“This heinous act once again underscores the urgent need for a political resolution to the conflict in Libya, the continuation of which only benefits terrorist groups, including Isil.”