The Maoists did not harm the workers of the private road construction, but drove them away and put up posters, the sources said.
The posters demanded immediate halt to operation green hunt, steps and investment in tribal welfare activities and release of tribals in jails charged with being Maoists, they said.
The attack came two days after the ultras gunned down a former naib sarpanch of Markapadar in the district suspecting him to be a police informer.