An ambush by militants of an opium poppy eradication force sparked clashes that killed 25 Taliban fighters and a policeman, a provincial police chief said Thursday. Four other militants died when a bomb went off. Insurgents ambushed the drug eradication force Wednesday in Marja district of Helmand province -the world's largest opium producing region -killing one police officer and wounding two, said Gen. Mohammad Hussein Andiwal, the provincial police chief. Police attacked the militants afterward, killing 25 Taliban fighters, Andiwal said. Separately, four militants died and another was wounded Thursday when the roadside bomb they were planting on a main road in Helmand province exploded prematurely, Andiwal said.