The attack occurred at Chakia, about 100km east of the Hindu holy town of Varanasi in the populous Uttar Pradesh state on Saturday. 

Chakia is near the border of neighbouring Bihar state where Maoist insurgents, claiming to be fighting for the rights of landless labourers and poor peasants, have a strong presence. 

"This is the first time the police in Uttar Pradesh have been attacked in such a gruesome manner and we are not going to spare them [the guerrillas]," VKB Nair, director-general of police, said. 

"The two injured policemen are in critical condition."

He said police reinforcements had been sent to Chakia and were scouring the area. 

Maoist fighters operate in southern and eastern India and often target the police through ambushes and by planting landmines. They are also active in Nepal, which borders both Uttar Pradesh and Bihar.