Police has opened fire in the air here at Mainpakhar of the district as a group of Tharuhat protesters attempted to attack at Mainpakhar-based Area Police Office on Friday. According to Binod Bahadur Kunwar, Chief District Police Officer, a clash ensued between police and protestors outside of the police office as protestors attempted to enter into the office. A head constable has sustained injury in the incident. According to an eyewitness, two demonstrators have sustained bullet injury in the incident. They have been ferried to Nepalgunj for the treatment.