Bearing the name of 'Malkangiri Adivasi Sangh', the posters have appeared in several remote areas of Kalimela and Padia blocks of the district since yesterday, they said.
The posters listed some killings including that of tribal village head of Darbaguda in Kalimela area, Bira Padiami in an IED explosion on July 29.
Killings of tribals like Ganga Madhi, Madan Hantal, Deba Padiami and Ganga Madkami recently were also cited by the 'Sangh'. The development was being closely watched, they said.
The posters carrying messages in Odia condemned the recent killings, particularly of tribal people who were accused by the assailants of working as informers of the police, Superintendent of Police Akhileswar Singh said.
Several posters have appeared in remote areas like Telrai, MV-37, Kalimela Hat, Padia, Bejangwada and Gamphagonda, the SP said.
The message conveyed through the posters clearly showed that the tribals were getting increasingly disillusioned and angry with the violence being perpetrated by the Maoists in the region, he said.