A bomb exploded and gunmen attacked a mosque in Egypt's North Sinai province during prayers on Friday (24 November), killing at least 235 and injuring more than 130.
Three Egyptian security officials told Associated Press that Isis-affiliated militants are behind the attack.
Following the explosion, extremists reportedly opened fire from four off-road vehicles on the al-Rawdah mosque in the town of Bir al-Abd, 40km (25 miles) from the provincial capital of el-Arish.
The mosque is attended by mainly Sufi Muslims, who have been targeted by Isis-affiliated militants before.
At least 235 people have been killed and some 130 have been wounded, a spokesperson for the health ministry told Egyptian TV.
The explosion comes just weeks after a major militant attack against Egyptian soldiers in Sinai. More than 50 soldiers were killed during a shootout with militants on 20 October.
In September, 18 policemen were killed in an attack on a convoy near al-Arish by Isis-affiliated militants.
Egypt has been fighting an Islamist insurgency since President Mohammed Morsi was ousted in 2013.
Isis-affiliated fighters have in the past targeted followers of the Sufi branch of Sunni Islam as well as Christians. More than 100 members of the Coptic Orthodox community have been killed since December by militants affiliated to Isis.