The World Health Organization on Tuesday played down the extent of an outbreak of the deadly Ebola virus suspected to have killed over 80 in Guinea, a day after medical charity Doctors Without Borders warned of an unprecedented epidemic.

Countries in West Africa — including neighbouring Sierra Leone and Liberia where suspected cases have also been detected — are scrambling to bring the outbreak under control, with many of them imposing health and travel restrictions.

Doctors Without Borders has warned they face an uphill task because the infections are scattered across several locations, most worryingly in Guinea's densely populated capital Conakry. It blasted governments and international public health organizations for not doing enough to tackle it.

However, the World Health Organization (WHO) said the number of suspected and confirmed cases in Guinea was unchanged from the previous day at 122, of whom 80 had died. In Liberia, there were seven suspected or confirmed cases, of whom four had died.

Asked if the spread of the disease was unprecedented, WHO spokesman Gregory Hartl said there had been much larger outbreaks in the Democratic Republic of Congo and Uganda.

"This is relatively small still. The biggest outbreaks have been over 400 cases," Hartl told a news conference in Geneva. He added it was not the first time Ebola had been reported in a capital city. It struck Gabon's Libreville in the 1990s.

"Ebola already causes enough concern and we need to be very careful about how we characterize something which is up until now an outbreak with sporadic cases," Hartl said.

However, Doctors Without Borders director general Bruno Jochum said it was remarkable the outbreak had spread to several places and to a city of around two million people, Conakry.

Spread to city

"These two characteristics make it an exceptional event for an Ebola outbreak up until today," Jochum said, adding that given the high mortality rates among identified cases, it should be taken extremely seriously.

Ben Neuman, a virologist at Britain's University of Reading, also said it was a real worry that the virus had spread from sparsely populated forest zones to Conakry, where population density was close to 10,000 per square kilometre. "An Ebola outbreak there could lead to a humanitarian disaster," he said.

Mariano Lugli, co-ordinator of Doctors Without Borders's project in Conakry, said on Monday: "We are facing an epidemic of a magnitude never before seen in terms of the distribution of cases in the country."

Jochum said at a separate news conference in Geneva on Tuesday that Doctors Without Borders and other organizations such as the Red Cross and Pasteur Institute had been active on the ground but the response from state authorities and international public health organizations has been minimal.

The outbreak of one of the world's most lethal infectious diseases has alarmed a number of governments with weak health systems, prompting Senegal to close its border with Guinea and other neighbours to restrict travel and cross-border exchanges.

Would close borders

Guinea, the hardest hit by the outbreak, had the lowest ratio of hospital beds per capita in a World Bank survey of 68 nations in 2011, with just 0.3 hospital beds per 1,000 people.

Liberia's Senate on Tuesday agreed that the government should declare a state of emergency that would lead to the closure of the country's borders.

"Liberia should close her borders with all the three countries which are sharing borders with us — Guinea, Sierra Leone and Ivory Coast," Senator Sando Johnson told Reuters.

Liberia's lower house of parliament is expected to debate the proposal on Thursday. If passed, it will be sent for approval to President Ellen Johnson Sirleaf.

Saudi Arabia's health ministry said in a statement it had recommended its government cease issuing visas to pilgrims from Guinea and Liberia as a precautionary measure, although the WHO has not yet requested any travel or trade ban on both countries,