The incident took place this afternoon when a woman took four children to the tank to wash clothes, said Jagadeeshwar Rao Circle Inspector of Police, Nekkonda.
The four children entered the tank and slipped into the water. The woman was successful in saving one child, while the other three drowned, the officer said.
The deceased were identified as G Ajay (10), G Sai (7) and Akhila (8). Their bodies were fished out of the tank, he said, adding a case was registered.