Pankaj Kumar, an aide of Mahto who was with him at the hospital, claimed that Mahto was injured during a police lathi-charge near the Jharkhand Assembly. Several protesters and four policemen were injured during a clash near the Jharkhand Assembly on Monday, officials said. Police used water cannons and tear gas and resorted to lathi-charge to disperse job aspirants protesting against alleged irregularities in recruitment examinations, they said.