Eighteen members of the police force were killed on Monday when militants ambushed a convoy in Egypt’s Sinai Peninsula. Seven others were wounded in the attack, said security and military officials.

The attack started with roadside bombs that destroyed and set ablaze four armored vehicles and a fifth one carrying signal jamming equipment. The gunmen later opened fire with machine guns and commandeered a police pickup truck.

Among those killed were two police lieutenants. The wounded included a police brigadier general. There was no immediate claim of responsibility for the attack, which bore the hallmarks of ISIS. The attack took place about 30 kilometers (nearly 19 miles) west of al-Arish in northern Sinai, the epicenter of a long-running insurgency now led by the terrorist group.

The officials spoke on condition of anonymity because they were not authorized to brief media. 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 and casualty figures.

Security forces were exchanging fire with militants near the explosion site and managed to kill several of them, MENA said. Monday’s attack was the deadliest against security forces since July, when ISIS terrorists attacked a remote army outpost in the border town of Rafah, killing 23 soldiers. That was the deadliest attacks in two years.