The dugongs, weighed between 250 and 500 kilogrammes, were captured and killed by local fishermen in Ha Tien town and Phu Quoc island in the southern province of Kien Giang, the Tuoi Tre newspaper said.

However, the WorldWide Fund for Nature's Indochina programme in Hanoi said they had only been informed of the death of one dugong in Phu Quoc, by local authorities.

The population of dugongs, a whale-like mammal found in shallow tropical waters from East Africa to Australia, has declined dramatically in the past 25 years in Vietnam, despite being listed in the government's conservation "red book".

Today, it is estimated that there are nearly 10 dugongs living in Con Dao island and as many as 100 others around Phu Quoc, Vietnam's largest offshore island.

Catching a dugong can prove extremely lucrative, with adults fetching more than 800 dollars or twice the national annual average income.

Born a pale creamy colour, dugongs darken with age. They can grow to around three metres (10 feet) in length.

Besides their meat, dugongs are also hunted for their oil, their hide and for medicinal purposes, particularly in Asia.

All dugongs are listed in the Convention on International Trade in Endangered Species (CITES) under the most at-risk category.

TERRA.WIRE