CAIRO - At least 306 people were killed when gunmen set off a bomb and opened fire at a mosque in Egypt's northern Sinai Peninsula on Friday, state television reported.
The report also said at least 125 people were wounded in the attack.
Egypt's government declared three days of mourning after the attack - one of the country's deadliest in recent memory.
Security officials said four men in four off-road vehicles opened fire on worshippers during Friday prayers at Al Rawdah mosque in Bir al-Abed, about 40 kilometers from the North Sinai provincial capital of el-Arish.
No group had claimed responsibility for the assault.
A tribal leader and head of a Bedouin militia that fights Islamic State extremists said the mosque is known as a place of gathering for Sufis.
The IS group views Sufis as heretics.
State media showed images of bloodied victims and bodies covered in blankets inside the mosque.
Eyewitnesses reported about 50 ambulances ferrying casualties from the scene to nearby hospitals after the attack.
"They were shooting at people as they left the mosque," said a local resident whose relatives were at the scene.
"They were shooting at the ambulances too."
President Abdel-Fattah al-Sisi convened an emergency security meeting soon after the attack. The meeting was attended by the ministers of defense and interior in addition to the heads of general intelligence and military intelligence services, MENA state news agency reported.