Egyptian President Abdul Fattah al-Sisi has vowed to respond with "maximum force" after 300 people were killed in a North Sinai mosque during Friday prayers.
The Egyptian army says it has carried out airstrikes on "terrorist" targets in response.
No group has yet claimed responsibility for the attack, the deadliest in recent years.
After the bombs exploded, dozens of gunmen waiting outside the mosque opened fire on those trying to escape.
The assailants reportedly set fire to parked vehicles to block access to the building and shot at ambulances trying to help the victims.
Thirty children are among the dead and at least 100 people have been injured.
Locals say the al-Rawda mosque is used by the local Sawarka tribe, which is known to co-operate with security services against militants.
Egypt's response
An army spokesman said "terrorist spots", where weapons and ammunition were stored, had been bombed by jets on Friday in response.
The official also said that various vehicles used for the attack had been located and destroyed.
Three days of mourning have been declared in the country.