ISIS forces fired a series of mortar rounds against an army post in the northern part of the Sinai Peninsula today, before attacking the checkpoint on the ground, killing at least 12 Egyptian soldiers and wounding six others.

An Egyptian military statement reported the ISIS forces attacked using four-wheel drives, and that Egyptian troops quickly reinforced the attacked checkpoint. They reported 15 ISIS fighters were slain in the fighting. ISIS has not issued a statement yet on the matter.

Egypt has been fighting an Islamist faction in Sinai for years, and the group declared itself an ISIS affiliate in late 2014. The group has been a major target since Egypt’s 2013 military coup, after which the junta accused the ousted elected government of being in league with the militants.

The operations in Sinai have been increasingly bloody, with the ISIS affiliate launching several high-profile attacks, including bombing a Russian passenger plane taking off from a Sinai resort, and killing 224 people.