A 30-year-old woman has died in the Liberian capital after contracting Ebola, officials said Friday, more than two months after the epidemic was declared over in the country.

"Lab results confirm a new case of Ebola virus disease in Liberia -- a 30-year-old woman who died yesterday afternoon while being transferred to a hospital in the capital Monrovia," the World Health Organization (WHO) said in a statement.

A Liberian health ministry official confirmed the case to AFP and said further details would be released later on the woman's death, with an emergency meeting convened to co-ordinate a response.

A resurgence of Ebola in a rural Guinean community has killed seven people in the last few weeks, but it is not known if the new Liberian case is linked.

The WHO said one of its teams and local experts were sent to the area near Monrovia where the woman was living and to a clinic that treated her.

They were to "begin case investigation and identification of individuals who may have been in contact," the statement said.

Liberia was the country worst hit by a two-year outbreak that saw 4,800 deaths. It discharged its last two Ebola patients from hospital in December, after which the country was monitored for 42 days before being given the all-clear.

The WHO had said on Tuesday that the Ebola outbreak in West Africa no longer constituted an international emergency, voicing confidence that remaining isolated cases in the affected countries can be contained. 

But a significant number of deaths are believed to have gone unreported and "flare-ups" relating to the persistence of the virus in survivors' bodies pose ongoing challenges. 

Ebola causes severe fever and muscle pain, weakness, vomiting and diarrhoea. In many cases it shuts down organs and causes unstoppable internal bleeding. Patients often succumb within days.

The virus is spread through close contact with the sweat, vomit, blood or other bodily fluids of an infected person, or the recently deceased.

The Liberian case comes as the WHO announced it had vaccinated 800 people in Guinea in the area where Ebola symptoms were reported among a family on March 16.

The family members had contracted Ebola from "a known transmission chain and not a new chain introduced by the animal population," the WHO said.

Liberia briefly closed its border with Guinea following the announcement of new cases there, but it has subsequently reopened, several Guinean sources confirmed to AFP.

The world health body has warned that sporadic recurrences of the deadly virus -- which has claimed 11,300 lives since December 2013 -- remained a possibility.

Neighbouring Sierra Leone announced beefed up security measures along with screening and surveillance points at all border crossings with Guinea on Thursday.

The deadliest period in the history of the feared tropical virus wrecked the economies and health systems of the three worst-hit west African nations after it emerged in southern Guinea in December 2013.