A deadly yellow fever outbreak in Angola, which has already spread the disease as far as China, risks sparking a global crisis, the Red Cross warned on Thursday.

The International Federation of Red Cross and Red Crescent Societies (IFRC) urged immediate action with health director Julie Hall warning that limited vaccine supplies, inadequate disease surveillance systems, poor sanitation and continuous movement across Angola's borders "could turn a national outbreak into a global crisis".

"Unvaccinated travellers could transform this outbreak into a regional or international crisis if we don't move quickly to protect vulnerable populations and help communities to reduce their risk of infection," she said in a statement.

The warning came as the World Health Organization was holding an emergency meeting Thursday on the Angola outbreak.

Such meetings from the UN agency are often held before the declaration of an international health emergency, as happened with the Ebola outbreak in West Africa, and the current surge in neurological disorders linked to the spread of Zika virus in the Americas.

Yellow fever has been raging since last December in Angola, and especially in the capital Luanda, killing 293 people in the country to date and infecting another 2,267.

Cases have been imported to Democratic Republic of Congo and Kenya, and the Angola outbreak has been proven to be the source of 11 infections in China.

A separate yellow fever outbreak has meanwhile been confirmed in Uganda, with more than 50 suspected cases.

There is no specific treatment for the viral hemorrhagic disease, transmitted by the Aedes aegypti mosquito, which also spreads Zika, dengue and chikungunya. 

The percentage of people immunised against yellow fever remains low in many parts of Africa, even though the vaccine is nearly 100 percent effective and relatively cheap. 

WHO has sent 11.7 million doses to Angola and there are plans to vaccinate 2.2 million people in DR Congo.

But it has voiced concern that the outbreak could easily spread to Angola's neighbours Namibia and Zambia, where the population has not been vaccinated.

National Red Cross societies in Angola, DRC and Uganda were meanwhile helping communities in affected areas identify and eliminate mosquito breeding grounds and advising people how to reduce their risk of infection, IFRC said.