THE death toll from the attack on an Egyptian mosque in the Sinai has been raised to at least 305, including 27 children.

It was carried out by 25 to 30 heavily-armed gunmen, some waving Islamic State flags, who arrived at the mosque in the small town of Bir al-Abd in five all-terrain vehicles before opening fire on worshippers inside.

The mosque is frequented by Sufi Muslims, a mystic school of Islam that Sunni militants consider heretic.

Survivors spoke of horrific scenes during the 20 minutes it took the attackers to kill and maim worshippers. They spoke of some jumping out of windows, a stampede in a corridor leading to the washrooms and of children screaming in horror. Some spoke of their narrow escape from a certain death, others of families that lost all or most of their male members.

After Egypt's President Abdel-Fattah el-Sissi vowed that the attack "will not go unpunished" the Egyptian military said their warplanes had targeted several vehicles yesterday in which some of the attackers were travelling. All passengers of the vehicles were killed, it added.

President el-Sisi also ordered a mausoleum be built in memory of the victims.

The military and security forces have been waging a tough campaign against IS groups and affiliates in the towns, villages and desert mountains of Sinai, and the country has been in a state of emergency since April.