At least 55 whales stranded on a beach near Cape Town were put down or died after rescue teams failed to return them to the ocean, a sea rescue institute said. Scientists shot 42 of the false killer whales ysterday and 13 others perished, possibly from internal injuries, at Kommetjie Beach, the National Sea Rescue Institute (NSRI) said.

"We don't know if any of those we managed to get back to the water had survived ... one of them just washed up at the rocks around the Kommetjie lighthouse this morning and this could continue over the week," spokesman Craig Lambinon said.

Marine scientists and volunteers worked all day to try to get the whales back into the water, but many were pushed back ashore by waves.

Rescuers had battled to keep the beached adults and calves wet and used earth-moving equipment to try to save them.

Lambinon said it was unclear why the whales had come ashore early in the day and it was the first mass beaching of whales he knew of on the popular stretch of coast.

He said tests would be carried out on samples from the carcasses to try to establish the reason for the beaching.

Rescue teams had contemplated taking the whales to a nearby naval base and transporting them on boats to the deep sea, but the idea was abandoned because the animals' condition deteriorated rapidly.

The NSRI first identified them as pilot whales, but said later they were false killer whales.

Whale-watching off South Africa's coast is a popular attraction with tourists, who often line roads at strategic spots to catch a glimpse of the giants of the ocean.