Another 50 percent are under imminent or long-term threat because of rising sea levels most scientists blame on global warming, the group said.

"The reefs help to feed millions of people in the developed world," the group's co-chairman Rolph Payet told reporters at the group's annual meeting in the Seychelles.

"Many species of fish depend on coral reefs for their food or protection and the collapse of the reefs would lead to elevated costs of fish worldwide," he said.

Although islands are perceived as the principal victims of coral degradation, Payet said it could affect many other countries worldwide.

"The threat to coral reefs is certainly not just an island problem because reefs, including the largest ones, border continents and large countries alike," said Payet, who is also a top environmental official in the Indian Ocean archipelago.

Payet urged industrialised countries "which contribute overwhelmingly to global warming" to commit more money to coral reef monitoring and management programmes.

ICRI has reported coral damage in almost 100 countries around the world, with some parts of the Indian Ocean so badly affected researchers fear large areas could be without any living coral within two decades.