"While we know about other threats such as over-fishing, hunting and pollution, a new and emerging threat to cetaceans is that of increased underwater sonars," Mark Simmonds of the Whale and Dolphin Society told Reuters.

"These low frequency sounds travel vast distances, hundreds if not thousands of kilometres from the source."

In October, a coalition of environmental groups sued the US Navy over its use of sonar, saying the ear-splitting sounds violated environmental protection laws.

The navy said it was studying the problem but said sonar was necessary for national defence.

Animal protection groups have for years lobbied to restrict the use of sonar, saying the sound blasts disorient the sound-dependent creatures and causes bleeding from the eyes and ears.

Simmonds said in recent years, western governments have developed stealthier submarines the detection of which requires more powerful, low-frequency sonars.

The report by the United Nations Environment Programme (UNEP) and the Convention on Migratory Species (CMS) says species like the Beluga whale, Blanville's beaked whale and the Goosebeak whale are seriously at risk.

Researchers found that a stranding of 12 Goosebeak whales in the Ionian Sea in the 1990s coincided with NATO tests of an acoustic submarine detection system.

Other Goosebeaks were stranded off of the Bahamas in 2000, and experts link that to military tests.

Tests on the bodies of seven whales that died near Gran Canaria in 2002 found haemorrhages and inner ear damage, which experts said was caused by high-intensity, low-frequency sonar used in the area.

"This is a hugely serious concern as these animals need sound to navigate, to find their food, to communicate and to mate," said Simmonds.

There are no laws governing noise pollution in the world's oceans, but western governments, considered largely responsible with their increased military presence in the seas, say they need more research before taking action.

Charles Galbraith, a senior wildlife advisor to the British government, told Reuters the report highlighted a potential problem. "But the issue is still in a relatively grey area in terms of scientific proof and we need to do more research before the government can review its defence systems," he said.