The US government is to begin testing an experimental Ebola vaccine on humans, after positive results from pre-clinical trials on monkeys.

The infectious disease unit of the country's National Institutes of Health is working with the US Food and Drug Administration to begin testing the drug as soon as possible.

The human trials could be underway as early as September, the NIH's Dr Anthony Fauci said.

The move comes as the death toll from the Ebola outbreak in Western Africa rose amid international concern about the spread of the deadly virus.

Ebola kills 90% of those who become infected, and there is currently no known cure or vaccine.