Cairo: The dreaded Islamic State released a grisly video showing the beheading of 21 Egyptian Coptic Christians in Libya, as Egypt today sent warplanes to bomb IS targets across the border in swift retaliation, pulling Egypt directly into the militancy-caused turmoil for the first time.
Egypt publicly acknowledged taking military action in Libya as warplanes targetted training camps and arms depots of the terror outfit at dawn and then in afternoon raids.
The country also sought international intervention in Libya against the IS and called on the US-led coalition fighting the militants in Iraq and Syria to broaden combat efforts to include the militants' new country of operation, highlighting how the terror group is expanding its reach around the Arab world.
Security officials said warplanes struck Libya's eastern coastal city of Darna and its suburbs during the second wave of air strikes. The first wave of air strikes also targetted Darna - an extremist stronghold - in the oil-rich nation, where civil unrest has created havens for factions.
The attack came as "retribution" to a gruesome five- minute online video released by the IS hours earlier that showed handcuffed hostages dressed in orange jumpsuits being murdered by black-clad masked terrorists at a beach near Libyan capital Tripoli.
"The sea you've hidden Sheikh Osama bin Laden's body in, we swear to Allah we will mix it with your blood," one of the militants says towards the end of the clip.
The beheadings, the first of its kind by the radical group outside the territory it controls in Syria and Iraq, drew immediate condemnation in Egypt, where President Abdel Fattah el-Sisi said on national television that his country "reserves the right to respond in the way and timing it sees fit for retribution from these killers."
He warned that Egypt would choose the "necessary means and timing to avenge the criminal killings".
Terming the beheading of the Christians as 'vicious', Sisi said a new series of terrorism is spreading across the world and demanded that all people come together to fight it.
"Your armed forces on Monday carried out focussed air strikes in Libya against Daesh (IS) camps, places of gathering and training, and weapons depots," the military said in a statement to Egyptians, shocked after the beheading.
"Avenging the Egyptian blood from killers and criminals is Egypt's enforceable right. This to let everyone know that Egypt has a shield that protects and safeguards its security and a sword that can cut off terrorism," army spokesperson Mohamed Samir said in the statement.
Civilians, including three children and two women, were
killed in the strikes, reports said, citing two Libyan security officials who were not named.
Nearly 50 militants were killed in the strikes that were were coordinated with the Libyan forces, Libya's air force commander Saqr al-Joroushi told Egyptian state TV, adding: "More air strikes will be carried out today and tomorrow in coordination with Egypt."
Egypt is battling a burgeoning Islamist insurgency centred in the Sinai Peninsula, where militants recently declared their allegiance to the IS. They rely heavily on arms smuggled across the porous border between Libya and Egypt.
Meanwhile, Sunni Islam's top body, Al-Azhar condemned the "barbaric" beheading of the Christian labourers, who were kidnapped from the coastal city of Sirte in December and January.
During his speech, Sisi offered his condolences to the families of the dead even as he ordered the government to ban Egyptians from travelling to Libya and facilitate the return of others from there.
Sisi called an urgent meeting of Egypt's top national security body to decide the course of action. He also asked the Foreign Minister to travel to New York and participate in the "fighting terrorism" summit.
Meanwhile, the UN Security Council in a statement also "strongly condemned the heinous and cowardly apparent murder" of the Christians.
UN Secretary General Ban Ki-moon denounced the killings, that raise the possibility that the militant group has established a direct affiliate close to the southern Italy.
A militant in the video makes direct reference to that possibility, saying the group now plans to "conquer Rome".
Earlier in the day, Egypt announced a seven-day mourning period over the beheading.
Egypt's Copts are the largest Christian community in the Middle East and are estimated to account for around 10 per cent of the Egyptian population.
Thousands of Egyptians have headed to Libya to work since the Egyptian uprising in 2011, despite their government's advice that they should stay away from the country.
The latest IS video comes after the militants released footage earlier this month showing the gruesome burning alive of a Jordanian fighter pilot besides beheading two Japanese hostages, drawing international condemnation and outrage.