Malda superintendent of police Prasun Bandopadhyay said the locals attacked policemen who went to Sultangunj village in Kaliachowk in plainclothes as part of a drive to destroy illegal opium cultivation.
The attackers threw stones at the policemen but none were injured, he said adding none of the police vehicles were damaged by the mob.
One policeman was held back by the protestors for some time but was later allowed to go, Bandopadhyay said.