Egypt bombards IS targets after 21 Egyptians beheaded in video

Egypt will choose the 'necessary means and timing to avenge the criminal killings', says President Abdel Fattah el-Sisi

The Islamic State released a grisly video showing the beheading of 21 Egyptian Coptic Christians in Libya, drawing swift retaliation from Egypt which launched air strikes in the neighbouring country, in an escalation of Egypt's battle against growing militancy.

For the first time, Egypt publicly acknowledged taking military action in Libya as warplans targetted training camps and arms depots of the dreaded outfit.

The attack came as "retribution" to a gruesome five- minute 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.

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 has condemned the "barbaric" beheading of the Christian labourers.