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.
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.
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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.
"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.