Congo will begin administering an experimental Ebola vaccine as the death toll from the latest outbreak continues to climb.

The vaccine will be rolled out at Mbandaka, the north-western city of 1.2 million recently struck by the outbreak, with 26 already dead.

"The vaccination campaign begins tomorrow, Monday, in Mbandaka, capital of the province," Minister of Health Oly Ilunga told The Associated Press.

"It will target, first, the health staff, the contacts of the sick and the contacts of the contacts."

Initially, the campaign will target 600 people, mainly medical staff, contacts of suspected cases, and those who have been in contact with the contacts, Ilunga said.

Members of a Red Cross team don protective clothing before heading out to look for suspected victims of Ebola, in Mbandaka. Picture: AP (AP)

Officials are working urgently to prevent the disease from spreading beyond Mbandaka, which lies on the Congo River, a busy traffic corridor, and is an hour's flight from the capital.

More than 4000 doses are already in Congo and more are on the way, according to officials. The vaccine is still in the test stages, but it was effective in the West Africa outbreak a few years ago.

A major challenge will be keeping the vaccines cold in this vast, impoverished, tropical country where infrastructure is poor.

Four new cases have been confirmed as Ebola, said the health ministry in a statement.

A total of 46 cases of haemorrhagic fever have been reported, including 21 confirmed cases of Ebola, 21 probable and four suspected.

Health workers are sprayed with chlorine after leaving the isolation ward to diagnose and treat suspected Ebola patients. Picture: AP (AP)

Congo President Joseph Kabila and his Cabinet have agreed to increase funds for the Ebola emergency to more than US$4 million.

The Cabinet also endorsed the decision to provide free health care in the affected areas and to provide special care to all Ebola victims and their relatives.

The spread of Ebola from a rural area to Mbandaka has raised alarm as Ebola can spread more quickly in urban centres. The fever can cause severe internal bleeding that is often fatal.

The risk of Ebola spreading within Congo is "very high" and the disease could also move into nine neighbouring countries, the World Health Organization has warned.

The WHO, however, stopped short of declaring the outbreak a global health emergency. WHO said there should not be restrictions to international travel or trade.

Visitors are screened for the Ebola virus at the Economic Community of West African States (ECOWAS) Parliament secretariat in Nigeria. Picture: EPA (EPA)

While Congo has contained several Ebola outbreaks in the past, all of them were based in remote rural areas. The virus has twice made it to Kinshasa, Congo's capital of 10 million people, but was effectively contained.