Death toll of a bomb and gun assault on a packed mosque in Egypt’s restive North Sinai province rose to 305 on Nov. 25, as the country mourned for its dead.

Warplanes struck militant hideouts in retaliation for the country’s deadliest attack in recent memory.

Special prayers were planned nationwide a day after gunmen detonated a bomb and mowed down worshippers fleeing the Rawda mosque in North Sinai, where security forces are battling the Islamic State of Iraq and the Levant (ISIL).

President Abdel Fattah al-Sisi declared three days of mourning and vowed to “respond with brutal force” to the attack, among the deadliest in the world since the September 11, 2001 attacks on the United States.

“The army and police will avenge our martyrs and return security and stability with force in the coming short period,” he said in a televised speech.

Hours later Egyptian air force jets destroyed vehicles used in the attack and “terrorist” locations where weapons and ammunition were stocked, an army spokesman said.

The state prosecutor’s office said in a statement that 235 people were killed and 109 wounded in the assault on the mosque roughly 40 kilometers west of the North Sinai capital of El-Arish.