Water was released from the Krishnaraja Sagar (KRS) reservoir to Tamil Nadu around midnight, BJP and Kannada outfits alleged on Saturday.
Kannada activist Vatal Nagaraj condemned the alleged release and said his organisation, Kannada Chalavali Vatal Paksha, will lay siege to the KRS dam in the next two days.
The release follows the Cauvery Water Management Authority's direction to Karnataka to release 12,000 cusecs of water daily to Tamil Nadu for 15 days, according
to BJP Mandya unit spokesperson Manjunath.
The Krishna Raja Sagar dam is located in Mandya district. "The water was released from KRS around midnight. The water level in the Cauvery river has increased following the release," Manjunath told media.
This is happening despite the state government's earlier position that it would not release water to Tamil Nadu amid concerns over availability for farmers and drinking-water requirements, Manjunath alleged.