It is caused by a spore-forming bacterium, Bacillus anthracis, which survives for decades in soil where animals that died of anthrax or were carriers were buried. It is transmissible to humans and potentially fatal in its inhaled form.

The hippopotamuses were found floating in a river south of Lake Edward, which separates the DRC from Uganda, park director Emmanuel de Merode said.

The local office of the Congolese Institute for Nature Conservation (ICCN) in the North Kivu province, where the hippos were found floating, recommended precautionary measures including avoiding eating bushmeat.

"Although this disease mainly affects wildlife, it poses a potential risk of transmission to humans as well as domestic animals," said the body, which manages national parks in the DRC.

Virunga was established in 1925 and is renowned for its wildlife, particularly mountain gorillas, and magnificent landscapes.

It is also located at the heart of the conflicts that have been tearing the eastern DRC apart for the past 30 years.

Hippopotamuses and other mammals have already fallen victim to anthrax several times in Virunga and other nature reserves in Africa.