Security officials have told news agencies that Friday's attack happened at an army post near El-Arish, the main town in the restive northern region of Egypt's Sinai Peninsula.

The bombing killed 25 people - making it one of the deadliest attacks on security forces since a spike in violence following the ouster of Islamist former president Mohammed Morsi last July.

Jihadists in Sinai have killed dozens of policemen and soldiers since his overthrow, in order to avenge a crackdown on his supporters by the government.

The death toll from Friday's attack is expected to rise, as up to 20 people sustained serious injuries.

There is conflicting information about the attack. One Sinai official said it was not a car bomb, instead a rocket-propelled grenade operation.

Egyptian President Abdel Fattah el-Sissi's office has labeled it a "terrorist attack," with the president calling an emergency meeting of the country's National Defense Council.

jr/es (AP, Reuters, AFP)