Just hours after the World Health Organisation announced an end to the Ebola outbreak in West Africa, Sierra Leone confirmed a new death from the virus.

Swab tests carried out on a body by British health orgainsation Public Health England came back positive in the Tonkolili district, east of Freetown, a spokesperson said late on Thursday.

Sierra Leone was declared Ebola-free on 7 November and the entire region was declared free of the virus by WHO on Thursday when Liberia was cleared.

Neither the gender nor the age of the deceased person was released and it is not clear how many people the patient had come into contact with before the virus was detected.

Health officials in Freetown are now urgently looking for those who had come into contact with the victim, according to Umaru Fofana of the BBC.

The tests reinforce concerns about flare-ups of the virus that has killed more than 11,300 people since 2013 in the world's deadliest outbreak of Ebola.

WHO warned on Thursday that despite the absence of known transmissions of the disease in over two months, there could still be cases of Ebola in the region. Survivors can carry the virus for months and pass it on.

WHO on Friday confirmed the new Ebola case in Sierra Leone but did not immediately provide details or say whether there was a risk of others being infected.

While it has said that another major outbreak of the disease is unlikely, it reiterated its message of caution.

"WHO stresses ongoing risk of flare-ups due to the re-emergence of the virus throughout 2016 due to persistence of the virus in the survivor population," a spokesman said

Additional reporting by Reuters.