President Abdel Fattah al-Sisi said on Sunday that Egypt reserved the right to respond in a way it sees fit to the Islamic State's beheading of 21 Egyptians in neighbouring Libya.
Sisi warned Cairo would choose the "necessary means and timing to avenge the criminal killings".
He was speaking on national television hours after Islamic State released a video purportedly showing the beheading of 21 Egyptian Christians in Libya.
