Former Dravida Munnetra Kazhagam minister and two-time member of Parliament, T Kiruttinan, was killed when he was returning to his K K Nagar residence in Madurai after a walk on Tuesday morning, police said.
Family members, who heard his cries, rushed out of the house and saw him lying in a pool of blood. He was taken to a hospital, where he was pronounced dead, the police said.
The former minister is survived by his wife, a son who is employed in America and a daughter, residing at Chennai.
Kiruttinan, who was zonal-in-charge of Sivaganga and Madurai districts, had had hectic discussions about the DMK's organisational elections till late Monday night.
He had represented the DMK in both the Rajya Sabha and Lok Sabha.
There was tension in K K Nagar as news of his death spread and supporters gathered at his house.
DMK president M Karunanidhi expressed deep shock at the murder. "I cannot believe that Kiruttinan is no more as I spoke to him over telephone only last evening..." he said in a condolence message.
Party flags will fly at half-mast for three days as a mark of respect to the departed leader. All party functions have also been cancelled for this period.