The number of whales who have died after they were stranded on a beach in the southern Indian state of Tamil Nadu has risen to 73, officials said.

Thirty-six whales were rescued and pushed back into the sea at Tuticorin on Tuesday, but 28 of them floated back to the shore and died on Wednesday.

Earlier, 45 whales died after 81 of the animals were stranded on Monday.

The last time such an incident occurred in Tuticorin was in 1973 when 147 whales died.

Local fishermen, helped by officials, have been using mechanised boats to float the stranded whales back into the sea, but many of the animals have returned to the shore, BBC Hindi's Imran Qureshi reports.

"This is a well known phenomenon. When there is mass stranding, whales return ashore. Pilot whales are very social animals and they live in groups. They are very aware that some of their group members are in distress on the shore, possibly dead, so they don't wish to go back into the sea," whale expert Dr Kumaran Sathasivam said.

The dead whales are being buried near the shore at Tuticorin, officials say.