At least 18 Egyptian policemen were killed and three injured on Monday in an attack claimed by Islamic State on a security convoy in the Sinai Peninsula, which is gripped by an insurgency.

Axar.az reports citing Reuters that, security and medical sources said the attack took place near Arish, the capital of North Sinai province, and that two of those killed were officers. The injured included a brigadier general who lost a leg in the blast.

Militants detonated an improvised explosive device and managed to destroy three armored vehicles and a signal-jamming vehicle. The attack later turned into a gunfight and the militants also shot at ambulance workers, injuring four.

Islamic State claimed responsibility for the attack in a statement posted by its news agency Amaq.

The Sunni militants are waging an insurgency in the rugged, thinly populated Sinai. They have killed hundreds of soldiers and police since 2013, when the military ousted Egypt’s Islamist president Mohamed Mursi after mass protests against his rule.

At least 23 Egyptian soldiers were killed when suicide car bombs tore through two military checkpoints in North Sinai in July, in one of the bloodiest assaults on security forces in years.

There was no immediate comment from the Interior Ministry on Monday’s attack. State news agency MENA quoted a high ranking ministry official confirming the attack took place.

Security forces were exchanging fire with militants near the explosion site and managed to kill several of them, MENA said.