According to reports, Armstrong was attacked when he was entering his house on Sadayappan Street in Perambur at around 7.30 pm. on Friday. He was taken to a private hospital where he was declared dead on arrival.

"After committing the crime, the attackers fled from the spot," an officer said, adding that police have launched a search to nab the accused.

Armstrong, a lawyer by profession and known as the Dalit voice in the state, had previously served as a councilor in the Greater Chennai Corporation.

More information is awaited.