Increased naval military maneuvers and submarine sonars in the world's oceans are threatening dolphins, whales and porpoises that depend on sound to survive, a United Nations report said Wednesday.

The report concluded that the use of powerful military sonar is harming the ability of 71 types of cetaceans -- whales, dolphins and porpoises -- to communicate, navigate and hunt.

The report, by the U.N. Environment Program and the Convention on Migratory Species, said species such as the beluga whale, Blainville's beaked whale and the goosebeak whale are 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 hemorrhages and inner-ear damage, which experts said was caused by high-intensity, low-frequency sonar used in the area.

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

The Navy said it was studying the problem but said sonar is necessary for national defense.

Animal-protection groups have lobbied to restrict sonar, saying the sound blasts disorient the sound-dependent creatures and cause bleeding from the eyes and ears.

There are no laws governing noise pollution in the 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 adviser to the British government, said, "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 defense systems."