A man with a toy gun was detained at the entrance of the venue of a farmers rally in Karaikudi where Congress President Sonia Gandhi addressed a rally.
Sivashanmughavel was found carrying a "pistol" when he was frisked near the metal detector frame installed at the entrance, they said adding initially there was some confusion about the nature of the gun.
A sub-inspector shouted "it is a loaded gun" after which Sivashanmughavel was whisked away by police. A senior police official later said it was a toy gun.
The man was later identified as a Congress worker from Thiruthuraipoondi. He was taken to the security cabin where he was questioned by the special intelligence unit personnel and Superintendent of Police Thirugnanam.
The incident took place before Gandhi was to arrive to address the rally in the Parliamentary constituency of Finance Minister P Chidambaram.