Police said activists of the Periyar Dravida Kazhagam (PDK) also smashed flower pots and damaged the notice board, a clock besides the ashram emblem atop the main gate, they said.
They also raised pro Tamil slogans, police said, adding that the exact reason for the attack was not known.
Ashram sources said the attackers hit the watchman on the head before forcing their way into the Ashram. No devotee was present inside as the visiting time had ended, they said.
Cases were registered against them under various sections of the IPC relating to unlawful assembly, causing hurt and damage to property, they said.