45-year old M G Kathiresan along with his two children was returning here from his native village late last night when the gang waylaid his car and attacked them with sharp-edged weapons at Nedungulam in the district.
Kathiresan, his 9-year son and the driver were killed in the attack while his seriously injured daughter (7) had been admitted to the Government Rajaji Hospital in Madurai, police said.
Kathiresan had enemity with some local people during the local body elections last year, police said, adding the motive behind the murder was under investigation.
District Superintendent of Police Pannerselvam, who visited the murder spot around midnight last night, said all check-posts in the region had been alerted and a special team formed to nab the assailants.
In Chennai, Chief Minister and AIADMK supremo Jayalalithaa condoled the death of three and said stern action as per law would be taken against the perpetrators of the crime.
Stating that Kathiresan was murdered because of previous enmity, she announced Rs two lakh relief to his family and Rs one lakh to the kin of the driver from the party funds.
In a statement, she also said the AIADMK would bear the medical expenses of Kathiresan's daughter.
