They were demanding "immediate arrest" of Kurukshetra MP Naveen Jindal, whose name has cropped up in connection with the coalgate scam.
The police claimed that the activists threw some black chemical on them in front of the Jindal house in which six policemen, including a DSP Sidharth Dhanda were injured.
After that the police used lathicharge to control the crowd.
BJP district president Kamal Gupta, who was seriously injured in the baton charge, was admitted to a private hospital, sources said.
The protesters also threw black chemical on the main gates of the Jindal House, the industrialist MP's local residence here, and tried to enter it, but police prevented them from doing so.