Twenty-nine Taliban rebels allied with opium farmers in southern Afghanistan were killed when they tried to attack government poppy eradication missions, police said Thursday.

Four were killed early Thursday when a landmine they were planting in a road in Helmand province exploded early, provincial police chief General Mohammad Hussein Andiwal told AFP. The mine had been intended for a poppy eradication team in the province's remote Marja district.

Police clashed with militants for six hours on Wednesday in the same district, leaving 25 rebels dead, he said. "Police went to support the eradication. The six-hour fighting killed 25 Taliban and two Taliban were arrested," Andiwal said.

A spokesman for the hardline Taliban movement, Yousuf Ahmadi, confirmed that Taliban fighters were involved but said only one was killed.

Helmand is the centre of Afghanistan's drugs industry, which produces more than 90 percent of the world's opium, the main ingredient of heroin.