A fourth Sierra Leonean doctor, a woman, died Sunday after contracting the dreaded Ebola virus, a top health official said, while a Dutch charity repatriated two doctors suspected of having been contaminated with the disease.

Doctor Olive Buck, who was in charge of Lumley Government Hospital in the Sierra Leonean capital, tested positive for Ebola on Tuesday and was admitted to the Connaught Hospital in central Freetown.

"It's another sad loss for the profession," the country's chief medical officer Brima Kargbo told AFP by telephone. "The ministry of health is in deep grief to miss another devoted Ebola fighter."

At the same time, two Dutch doctors who may have been contaminated with Ebola at a clinic in Sierra Leone have been repatriated to the Netherlands, a spokeswoman for the foundation they work for said Sunday.

The doctors have been placed in quarantine at a hospital in the western city of Leiden where they are undergoing tests to confirm whether or not they have the disease, she said.

Patients of the late doctor Buck, who was in her early sixties, described her as "very friendly and jovial".

"This is a big blow. She was much loved for her caring spirit. I cannot believe that she had died," said 35-year-old Joko Sutton, one of her patients.

Buck is the first female doctor to die from Ebola in Sierra Leone. Three male doctors have succumbed to the tropical virus since July. Some 50 nurses in the country have also died from the disease.

Sierra Leone's emergency services also announced they had sent more teams to assist in burying those who died from Ebola in the west of the country, including the capital Freetown, to reduce the delays in funerals for the victims.

The Ebola outbreak ravaging west Africa has killed more than 2,400 people since it erupted earlier this year, according to the World Health Organization.

Sierra Leone, Guinea and Liberia are the hardest-hit countries.

The World Food Programme said Sunday it has stepped up its assistance to the three countries grappling with the worst-ever outbreak of Ebola.

The UN food agency said it wanted to "support the 353,000 people in the zones most affected by the Ebola crisis... to prevent this health crisis from becoming a food crisis."

In Liberia, President Ellen Johnson Sirleaf's office said Sunday that she had sacked 10 senior government officials who defied an order to return to the west African nation to lead the fight against the deadly outbreak.

"These government officials showed insensitivity to our national tragedy and disregard for authority," her office said in a statement.