A woman who was Liberia's sole remaining known Ebola patient has died at a treatment centre in the capital, said Francis Ketteh, acting head of the country's Ebola response team.

The case was Liberia's first in weeks and it set back efforts to halt a virus that has killed more than 10,000 people in Liberia, Guinea and Sierra Leone.

Authorities say the woman, who died in Monrovia on Friday, may have contracted Ebola through sex with a survivor, the Reuters news agency reported.

"We have been able to trace the people she came in contact with," Ketteh said. "We call on everyone to follow the Ebola preventative measures."

Before the woman fell ill, the Liberian government had hoped to declare the country Ebola-free next month, 42 days after the last patient tested negative for a second time, which would mark double the length of the virus's incubation period.

Health officials have warned the general population that even after areas are declared free of the disease, new cases are possible through sexual transmission. Liberia remains vulnerable to cases imported from Guinea and Sierra Leone.

Starting on Friday, Sierra Leone's six million people were being confined to their homes for three days as nation resorted again to a sweeping shutdown in a final push to stamp out Ebola. Sierra Leone President Ernest Bai Koroma vowed to do "whatever it takes" to get to zero cases.

Guinea has reported a rash of new cases of the disease, which had appeared to be on the wane.