Egyptian security officials say four civilians have been killed when a mortar shell hit their tractor in the turbulent northern part of the Sinai Peninsula.

The officials say a fifth civilian was wounded in Tuesday's attack in el-Arish, Sinai's largest city on the Mediterranean coast. The officials spoke on condition of anonymity because they are not authorized to talk to reporters.

Mortar shells fired by militants frequently kill or wound civilians in el-Arish.

Egypt has been battling militants in Sinai for years in an insurgency that intensified after the military's 2013 ouster of an Islamist president, Mohammed Morsi.

The insurgency is led by a local affiliate of the extremist Islamic State group.

Egypt is also facing a growing number of attacks by militants in its Western Desert.