Ramesh, son of AIADMK Chintamani ward secretary Boominathan, was coming with his friend Pandi and father in an autorickshaw when the gang, who were also in an auto, waylaid and attacked them, they said.
While Ramesh (20) died on the spot, Pandi and Boominathan were injured.
Police suspect that the attack could be to avenge the murder of one Manoharan, who was the AIADMK ward secretary of the same area two months ago during local body elections when there was some dispute over allocation of seats.
Four persons, including Ramesh, Pandi and Boominathan, had been arrested in connection with the murder,and they were out on bail.
They were on way to Tiruparankunram Police station to sign-in as part of the bail condition when the attack took place.