Militants of the Islamic State group have claimed responsibility for an attack Sunday that killed eight police officers south of the Egyptian capital of Cairo. A statement released by the militant group’s Egyptian arm reportedly called the attackers part of the “security unit of the caliphate soldiers,” who had since returned to their positions.

According to residents interviewed by Reuters, Sunday’s attack was carried out by gunmen wearing masks. The four attackers ambushed a van carrying eight plainclothes police officers in the district of Helwan — located on the outskirts of Cairo — and sprayed the vehicle with bullets from automatic weapons before fleeing the scene.

“Security troops are combing the area and making all efforts to arrest the criminals. All legal measures have been taken,” Egypt’s interior ministry reportedly said, adding that a lieutenant and seven other police officers were killed in the attack.

The gunmen are yet to be identified.

This is not the first time ISIS has claimed responsibility for attacks on security forces in Egypt, although most of them have been carried out in the sparsely populated Sinai Peninsula. The group is believed to be behind the bombing of a Russian airliner in October, an attack that killed all 224 people, most of them holidaymakers from the popular Red Sea resort of Sharm El-Sheikh.

Militants affiliated to the group have also claimed responsibility for several attacks in Cairo since 2013, which they say have been carried out in response to a police crackdown on supporters of deposed Egyptian leader Mohammed Morsi.