Cairo: Egypt raised its security alert to the highest level on Saturday as it emerged that the Islamic State may have been behind a mosque attack in the restive north Sinai in which more than 300 people died, the most lethal single assault in the country's recent history.

Hours after the midday attack on Friday, the military said it launched overnight airstrikes that destroyed vehicles believed to have been used in the gun and bomb attack on the mosque west of the city of Al-Arish.

There has been no claim of responsibility, but analysts said it bore the hallmark of an Islamic State affiliate that operates in the area and highlighted the challenges President Abdel-Fattah al-Sissi faces restoring security and reviving economic growth after years of upheaval since the 2011 Arab uprisings.

Initial investigations showed the attackers hoisted the Islamic State flag during the attack, which was carried out by 25 to 30 militants, the public prosecutor's office said in a statement.