The US ambassador to the UN has begun a visit to the three nations worst hit by the Ebola outbreak, criticising the level of international support so far.

Samantha Power has landed in Guinea and will visit Sierra Leone and Liberia.

She told NBC some nations who offered backing “haven’t taken responsibility yet” in supplying aid and doctors.

More than 10,000 people have contracted the Ebola virus, with 4,922 deaths, according to the World Health Organization’s latest figures.

All but 27 of the cases have occurred inside Sierra Leone, Liberia and Guinea.