Updated

Egyptian security officials say unidentified assailants have killed a policeman in a drive-by shooting in the country's north, the latest attack on security forces.

The Ministry of Interior, responsible for the police, said the on-duty officer had been riding his motorcycle Friday in the Nile Delta city of Mansoura when gunmen on another motorbike opened fire on him.

A series of bombings and assassinations, mainly targeting security forces and installations, have hit the country since the overthrow of Islamist President Mohammed Morsi in July.

Authorities largely blame the attacks on Islamic militants loyal to the ousted president. Violence initially surged last summer in the restive Sinai Peninsula before gradually spilling over into Nile Delta cities and the capital.