The Spanish missionary who contracted the Ebola virus in Liberia and was repatriated to Spain for treatment has died of the virus, health officials in Spain said on Tuesday morning.

Miguel Pajares, 75, arrived in Madrid last Thursday on a plane sent from Spain to Liberia, making him the first patient in the deadly outbreak to be evacuated to Europe for treatment.

Doctors said he was weakened and feverish, but in a stable condition. He was taken to Madrid's Carlos III hospital, where he was due to receive the experimental treatment ZMapp. A spokesperson from the hospital said he had died on Tuesday morning, but would not confirm whether he had received the treatment.

Pajares succumbed to the virus just as Liberia announced that it would be receiving doses of an experimental drug, believed to be ZMapp, to give to two doctors who tested positive for Ebola, making them the first Africans to receive the treatment in the fast-spreading outbreak.

The World Health Organisation said on Tuesday it backed the use of the experimental drug.

The news came as outrage grew that the drug had only been made available to two US citizens and Pajares, all of whom had been repatriated to their home countries for treatment.

In a statement, the California-based manufacturer of ZMapp, Mapp Biopharmaceutical, said it had run out of treatment after responding to a request from an unidentified west African country.

Pajares was one of three missionaries to test positive for the virus at the San José de Monrovia hospital in Liberia. All three had been helping to treat people infected with Ebola as part of their work with the San Juan de Dios hospital order, a Catholic humanitarian organisation that runs hospitals around the world. The two other missionaries, from Ghana and the Democratic Republic of the Congo, who were not evacuated, have also died of the virus in recent days.

Pajares arrived in Spain with Juliana Bohi, a nun born in Equatorial Guinea who holds Spanish nationality, who tested negative for the virus.