Over 400 people were today detained from across Punjab to thwart road block plans of farmers, who had called an agitation in protest against the arrest of their workers, even as a policeman died in Tarn- Taran while conducting raid at a hideout of union workers.

ASI Kulbir Singh, was part of a police team conducting raid at a hideout of farmers' union members in Jeowala village, intending to disrupt rail traffic and was killed at the wee hours yesterday, police said.

According to the police, when the team including the ASI reached the spot, they were held hostage by the farmers.

The farmers, however, alleged that the ASI was drunk and panicked after seeing a huge gathering of farmers. They claimed that the ASI ran away from the spot and later got a heart attack.

IG Border Range R P Mittal said it was difficult to ascertain the cause of the ASI's death till the autopsy report was received.

Police have so far arrested four persons in connection with the ASI's death.

Farmers tried to block roads at several locations across the state, but before they could put up blockades more than 400 activists, including several prominent leaders of the unions were taken into custody, an official spokesman said.

Criminal cases under relevant provisions of the IPC and the National Highway Act, 1956 were registered against them, Mittal added.