The incident left three injured, while thugs attacked a pregnant woman, said executive director of the organization Keerthi Tennakoon.
Police spokesman Ruwan Gunasekara said the area has returned to normalcy, while six men have been arrested on suspicion and remanded.
Hizbullah unsuccessfully contested the parliamentary polls, but he was appointed on the national list.
After the announcement was made, his supporters took to the streets, lighting firecrackers and staging processions.
The SLMC and the People’s Front for Good Governance said Hizbullah’s thugs assaulted their supporters in the streets and at their homes.
SLMC’s Mohamed Farook said 23, including a woman, were injured in Kathankudy.
Protests were staged in Colombo and Kathankudy yesterday, where the incident was condemned and the UPFA urged to cancel the MP position given to Hizbullah.
Commenting on this, Hizbullah said when his supporters were celebrating his appointment, SLMC and PFGG supporters provoked them.