Egyptian police shot dead four suspected Islamist militants inside a house a few miles from central Cairo, the interior ministry said on Sunday, the third such incident in as many weeks.

It said the men belonged to Ajnad Misr, a group that emerged in January 2014 and has targeted security forces in and around Cairo. The suspects had opened fire first, it said.

"Engagement resulted in the death of four known elements and the uncovering of an assault rifle, a 9mm pistol, an improvised firearm, a car previously used in many terrorist attacks, and a motorcycle without licence plates," a ministry statement said.

The men were suspects in the killing of two policemen, a soldier and a civilian and they were also suspected of blowing up a police vehicle and bombing a security checkpoint, it said.

Egypt is fighting an Islamist insurgency in Sinai that gained momentum in mid-2013 when the military ousted Muslim Brotherhood president Mohamed Mursi after mass protests against his rule. Hundreds of soldiers and police have been killed.

The Brotherhood says it is a peaceful movement but Egyptian security forces do not differentiate between it and groups such as Ajnad Misr and Islamic State.

Islamic State-affiliated militants sometimes carry out attacks in Cairo and other cities but are most active in Sinai, a strategic peninsula bordering Israel, Gaza, and the Suez Canal.

Police killed two men, suspected of being members of Ajnad Misr, at a Cairo apartment on Wednesday.

They also killed four suspected militants in three raids on Jan. 25, the fifth anniversary of the 2011 uprising that was in part sparked by rampant police brutality and that ended the 30-year rule of autocrat Hosni Mubarak.

The Interior Ministry says raids only occur with a warrant from a prosecutor, and that police do not shoot unless shot at.