Tensions surrounding the Ebola epidemic raging in west Africa sparked a deadly riot in Sierra Leone as the World Health Organization prepared Wednesday to coordinate clinical trials of an experimental vaccine against the killer virus.

Some 1,600 doses of the vaccine arrived in Geneva which the WHO, under fire for what has been seen as a lethargic response to the outbreak, hopes can be fast-tracked into "real-world use".

Meanwhile doctors said Wednesday two people died in a riot the day before in eastern Sierra Leone, which erupted when health workers tried to take a blood sample from a 90-year-old woman suspected of having Ebola.

Several buildings were attacked and gangs of youths roamed the streets shouting "No more Ebola!"

Sierra Leone and neighbouring Guinea and Liberia are the epicentre of the Ebola outbreak, the world's worst ever, which has killed more than 4,500 people including a handful outside the region.

Ebola crisis raises questions over air travel P. Deré/P. Defosseux, pld/abm/jfs/jj, AFP

Health teams are working desperately to slow the alarming spread of the virus, with experts warning the rate of infections could reach 10,000 a week by early December.

On Wednesday the WHO launched new emergency consultations connecting policymakers and health experts in Geneva and on the ground in west Africa by video and phone.

The third such talks since the WHO declared the outbreak an international crisis in August will likely last two days, with a news conference planned the day after they wrap up.

Some 1,600 doses of the experimental rVSV vaccine against Ebola arrived at the Geneva University Hospital on Wednesday from Canada.

The WHO is to coordinate trials of the vaccine in Geneva alongside those already under way in Germany, Gabon and Kenya.

Health workers wear protective gear at a Medecins Sans Frontieres Ebola treatment centre in Monrovia on October 15, 2014 Zoom Dosso, AFP/File

The vaccine, developed at the National Microbiology Laboratory in Winnipeg, is one of two experimental Ebola vaccines identified by the WHO as having shown promising results when tested on monkeys.

WHO assistant director general Marie-Paule Kieny said Tuesday the goal was to be able to ship initial supplies to Africa by early 2015, though mass vaccination campaigns are not yet on the cards.

"There is a very strong movement now from governments of many countries to push as quickly as possible these vaccines into real-world use," she said.

A key aim is to help guard health workers against Ebola -- some 240 have died so far as they strive to care for desperate patients.

Also Wednesday US pharmaceutical giant Johnson & Johnson announced it would spend $200 million (157 million euros) to accelerate an Ebola vaccine programme that is under development.

It plans tests on volunteers in January.

The Red Cross said it would be at least four months before the epidemic is contained, but only if all necessary steps are taken.

Medical staff, wearing protective masks, check health forms belonging to passengers arriving from Conakry in Guinea at the airport in Abidjan on October 20, 2014 Issouf Sanogo, AFP

"It will be possible, as it was possible in the past, to contain this epidemic within four to six months" if the response is adequate, said Elhadj As Sy, chief of the International Federation of Red Cross and Red Crescent Societies (IFRC).

"I think that is our best prospect," he said at an IFRC conference in Beijing. "There is always a price for inaction," he warned.

African Union chief Nkosazana Dlamini-Zuma, who arrived in the Ghanaian capital Accra on Wednesday ahead of a trip to the Ebola-hit west African nations, said that "a lot more needs to be done" in the campaign against the epidemic.

"We commend the ongoing continental and global efforts, but frankly, a lot more needs to be done to raise the needed resources considering the magnitude and rate of increase of the epidemic," she said in a statement.

Accra is the base of the United Nations Mission on Ebola Emergency Response (UNMEER).

Barbara Smith from Mount Sinai Health Systems demonstrates the proper technique for donning and removing protective gear during an Ebola educational session for healthcare workers at the Jacob Javits Center in New York on October 21, 2014 Timothy A. Clary, AFP

Havana announced that 83 doctors and nurses left Cuba late Tuesday for Guinea and Liberia, bringing to 256 the number of medical workers it has sent to fight the Ebola outbreak.

- New US measures -

The United States tightened restrictions on travellers from the three hard-hit countries, funnelling them into five airports with extra health checks.

There are no direct scheduled flights to the United States from Liberia, Sierra Leone or Guinea, but travellers from the region can transfer through African and European hubs.

A number of US lawmakers from both parties insisted the measures did not go far enough. They sought a suspension of visas from the three countries, while some urged a 21-day quarantine for Americans exposed to Ebola.

Experts writing in The Lancet medical journal on Tuesday said that screening air travellers on departure was a better option than monitoring them when they arrive abroad.

The central African country of Rwanda meanwhile ordered travellers who have been in the United States and Spain -- one Ebola patient has died in each country -- to send daily updates, the health minister said Wednesday.