Palestinian authorities say they have launched an investigation into the alleged beating death by West Bank police of a Palestinian man accused of killing two officers.

Palestinian police have been conducting arrest raids in the city of Nablus to apprehend suspects wanted over arms and drug sales.

Last week, two suspects were killed in a shootout and two policemen were killed in an ambush. The man blamed for the policemen's deaths, Ahmad Halaweh, was later arrested and according to Akram Rajoub, the Nablus governor, police beat the man to death in prison.

Prime Minister Rami Hamdallah said on Tuesday that authorities were investigating Halaweh's death.

Critics charge that Palestinian police have used heavy-handed tactics against suspects, though killings of suspects by police are rare.