An Egyptian riot police officer stands guard in Cairo, April 15, 2016. Mohamed el-Shahed/AFP/Getty Images

Unidentified gunmen killed eight policemen dressed in civilian clothes, including an officer, in an attack on a police vehicle in Helwan, just south of Cairo, the Egyptian Interior Ministry said on Sunday.

The ministry said in a statement on its official Facebook page that four gunmen with automatic weapons got out of a small pick-up truck, stopped the police car, sprayed it with bullets and then fled.

Residents told Reuters the gunmen wore masks. There was no immediate claim of responsibility for the attack.

Egypt is facing an insurgency, mainly based in North Sinai, that has killed hundreds of soldiers and policemen since mid-2013, when then-army chief Abdel Fattah al-Sisi ousted Islamist President Mohamed Mursi after protests against his rule.

While the deadliest attacks take place in Sinai, militants have targeted security forces and planted bombs in Cairo and other cities.