An outbreak of the deadly Ebola virus in the Democratic Republic of Congo risks spreading to major towns if not brought under control soon after the death toll doubled within a week, the World Health Organisation has warned.

The number of people killed by the contagious virus for which there is no known treatment has now risen to 31, including five health workers. Ebola causes massive bleeding and kills up to 90 per cent of its victims.

"The epidemic is not under control. On the contrary the situation is very, very serious," Eugene Kabambi, a WHO spokesperson in Congo's capital Kinshasa, said on Thursday. 

Towns 'threatened'

"If nothing is done now, the disease will reach other places, and even major towns will be threatened," he said, adding that an estimated $2m had to be urgently found to pay for measures to tackle the disease.

The outbreak, which is believed to have been caused by tainted bushmeat hunted by local villagers, has so far struck in
the towns of Isiro and Viadana in the northeastern province of Orientale.

Some 16 people in neighbouring Uganda died of the disease last month, though the WHO said the two epidemics were not connected.

The latest WHO figures show there are now 65 probable or suspected cases of Ebola in Congo, with 108 people under
surveillance.

Kabambi said one suspected case in Kinshasa had come back negative. Congo's ramshackle capital is home to at least nine million people and its health sector is crumbling.

Congo's infrastructure has been devastated by decades of corruption, conflict and misrule. The country last year came
bottom of a United Nations development index.