Egypt says it has bombed Islamic State targets in Libya, hours after the group published video showing the apparent beheadings of 21 Egyptian Christians.
State TV said the dawn strikes had targeted camps, training sites and weapons storage areas.
Libyan officials said Egypt had hit targets in the militant-held city of Derna in co-ordination with Libya.
A video emerged on Sunday showing militants forcing a group of men to the ground and decapitating them.
IS militants claim to have carried out several attacks in Libya, which is in effect without a government.
The kidnapped Egyptian workers, all Coptic Christians, were seized in separate incidents in December and January from the coastal town of Sirte in eastern Libya, under the control of Islamist groups.
The video of the beheadings was posted online by Libyan jihadists who pledge loyalty to IS. It was one of the first such videos to come from an IS group outside its core territory in Syria and Iraq.
The video describes the Copts as "crusaders" and refers among other things to two women, wives of Coptic priests, whose alleged conversion to Islam triggered a sectarian dispute in Egypt in 2010.