The bodies of Bijay Mahto, Manik Mahto and Brihaspati Mahto, bearing bullet wounds, were found in front of a college at Sebaytan village on Thursday morning, said the police.
A note, believed to have been left behind by the Maoists near the bodies, said the men were accorded the 'extreme punishment' by 'people's verdict' as they had acted as police informers. The police said the three victims had been called out of their homes at approximately 1.30 am and had been gunned down.
The body of a fourth person, Robi Mahto, bearing bullet wounds, was found at around noon at Salgeria village in Salboni area. A note allegedly left by the Maoists was found near the body too.
The man, who had given himself up to the Maoists, had been called out of his home on Wednesday night and killed.
In another incident, the Maoists blew up a beat office of the forest department at Jhitka using a landmine, the police said.