At least three civilians were killed and 22 people were injured late Sunday when a rocket slammed into the restive Sinai Peninsula, Egyptian medical sources said.

Witnesses told AFP the rocket fell outside a shop in the south of El-Arish, capital of north Sinai.

Security forces are struggling to quell an Islamist insurgency that has killed scores of soldiers and policemen in the peninsula bordering Israel and the Palestinian Gaza Strip.

The attacks surged after the military overthrew Islamist president Mohammed Morsi last year, and the militants extended their reach to the Egyptian mainland with a series of bombings.