Gunmen in the southern Iraqi city of Basra kidnapped then killed 15 policemen working as instructors at the local police academy, along with two translators, police said.
The men were forced off a bus on the city's outskirts at about 4:00pm (1300 GMT), said a local police captain, speaking on condition of anonymity according to guidelines protecting their identities.
Police began discovering their bodies dumped in several locations around the city about four hours later.
Basra is about 80% Shiite, Iraq's majority sect who make up the bulk of the police and security forces nationwide, especially in the predominantly Shiite south.
Most of the murdered policemen were also believed to be Shiite.