Egypt’s President Abdul Fattah al-Sisi has vowed to respond with “the utmost force” after 300 people were killed at a North Sinai mosque during Friday prayers.
The al-Rawda mosque in the town of Bir al-Abed was bombed and fleeing worshippers were then gunned down.
The Egyptian military has said it has conducted air strikes on “terrorist” targets in response.
No group has yet claimed the attack, the deadliest in recent memory.
After bombs were set off, dozens of gunmen waiting outside the mosque opened fire on those trying to escape.
The assailants reportedly set parked vehicles on fire in the vicinity to block off access to the building, and fired on ambulances trying to help victims.
Thirty children are among the dead and at least 100 people have been wounded.
The injured were brought to hospitals near and far, including in Cairo