The incident occurred yesterday in Balakhedi town when the groups clashed and someone from rival group opened fire, killing National People's Party worker Ramkishan Meena on-the-spot, SHO Mahuwa Satish said.
The body has been shifted to a nearby hospital, he said, adding that family members have refused to accept the body.
No arrests have been made yet, police said.
Additional forces have been deployed in the area to maintain law and order, they said.
In another incident, a woman was axed to death by a man of her village in Sriganganagar when she was walking towards polling booth to cast her vote, police said.
"Mahendra's daughter had eloped with Narendra's son and he wanted revenge, so he killed her when she was walking towards the polling booth," he said, adding that the accused has been arrested.