An enormous whale graveyard around 1,200km (745 miles) long has been discovered in the south-eastern Indian Ocean.

The site, which is 7km (four miles) deep, has been found in the Diamantina fracture zone, a range on the sea floor of ridges and trenches.

But it is the age of the remains - some from 5.3 million years ago - that has prompted huge excitement in the scientific community.

The underwater necropolis, which was discovered by a team of researchers from China, Italy and New Zealand, is teeming with organisms and species that "may be new to science", according to journal Nature.

One of the study's authors Xiaotong Peng of the Chinese Academy of Sciences said: "Discovering a necropolis of this scale was completely unexpected.

"The size of distribution, the depth and the age range were far beyond anything we had imagined."

During 32 dives to the site, explorers collected samples from 485 whale-fossil sites and active whale falls, and found a treasure trove of remains, including one extinct whale's skeleton.

The beaked Pterocetus benguelae, which is 5.3 million years old, was discovered to be one of the fossilised skulls in the graves.

A five-metre long Antarctic minke whale's carcass was the largest discovery made.

A new species which the team has called Pterocetus diamantinae, after the site, was also uncovered.

Jellyfish, worms and crustaceans are among the community of creatures living off the huge spread of carcasses.

"Peng and colleagues' encounter with a vast fossil graveyard is a truly unique discovery," Stephen J Godfrey of the Calvert Marine Museum wrote in Nature.

"Although the site has limited accessibility, it seems likely to hold many other exciting finds, and it will no doubt inspire more submersible dives in similar environments.

"Peng and colleagues' paper reminded me of a trailer for the first in a series of epic movies. I hope that there will be many more of these blockbusters to come."