The clash broke out in Abbotabad district of Khyber Pakhtunkhwa after both the groups accused each other of rigging during the local bodies elections.
The activists of PTI and PML-N of Dhamtour Union Council were going to Returning Officer's office to lodge their reservations over election rigging in the union council when the clash erupted, officials said.
When the activists of both the parties met in Fawara Chowk, they started raising slogans against each other and exchanged fire in which three people, including two brothers, believed to be PTI activists were killed.