A doctor from Sierra Leone who was being treated for Ebola in the US, the Nebraska Medical Centre, where the patient was being treated, has said.
"We are extremely sorry to announce that the third patient we have cared for with the Ebola virus, Dr Martin Salia, has passed away as a result of the advanced symptoms of the disease," said the hospital in a statement.
The hospital said it had "tentatively" scheduled a news conference for 11am (17:00 GMT) to brief reporters.
Salia, a native of Sierra Leone and a US resident, was infected with the deadly hemorrhagic fever while treating patients in his home country.
He was flown to Nebraska for treatment on Saturday.
The hospital said late on Sunday that Salia was in "extremely critical" condition and that doctors were doing everything they could to save him.
Salia was the 10th person with Ebola to be treated in the US, and the second to have died from the infection.
In October, a Liberian man, Thomas Eric Duncan, died at a Texas hospital of the virus which has killed thousands of people in West Africa in history's largest ever outbreak.
The World Health Organisation said on Friday that 5,177 people are known to have died of Ebola across eight countries, out of a total 14,413 cases of infection emerged since December 2013.