Israeli Prime Minister Benjamin Netanyahu called Saturday for countries to unify their efforts against "terrorism" as he condemned an attack on a mosque in Egypt that left 305 people dead.

"Israel strongly condemns the horrific and criminal terrorist attack on the Rawda mosque near El-Arish," said a statement from his office.

"Terrorism will be defeated even more quickly if all countries work against it together."

Egypt was in mourning on Saturday as the death toll from the gun and bomb assault at the mosque in the Sinai Peninsula soared above 300, including children, in the deadliest attack the country has witnessed.

The state prosecution said that up to 30 militants in camouflage flying the Islamic State group's black banner had surrounded the mosque and proceeded to massacre the worshippers during weekly Friday prayers.

The army said warplanes attacked militant hideouts in the insurgency-wracked North Sinai in retaliation.

IS has not claimed responsibility for the attack, but it is the main suspect as the mosque is associated with followers of the mystical Sufi branch of Sunni Islam whom it has branded heretics.

Source: AFP