The death toll from Ebola in the three worst-affected countries in West Africa has risen to 7,373 among 19,031 cases known to date there, the World Health Organization said on Saturday.

The latest data, posted overnight on the WHO website, reflected nearly 500 new deaths from the worst ever outbreak of the hemorrhagic fever in Guinea, Liberia and Sierra Leone since previous WHO figures were issued on Dec. 17.

Sierra Leone accounts for the most cases, 8,759, against 7,819 for Liberia. But Sierra Leone's death toll of 2,477 is far less than 3,346 recorded in Liberia, leading some experts to question the credibility of the figures reported by Freetown.

Sierra Leone's government this week launched a major operation to contain the epidemic in West Africa's worst-hit country.

President Ernest Bai Koroma said on national television that travel between all parts of the country had been restricted as part of "Operation Western Area Surge", and public gatherings would be strictly controlled in the run-up to Christmas.

Sierra Leone's leading doctor, Victor Willoughby, died of Ebola on Thursday, hours after the arrival in the country of an experimental drug that could have been used to treat him, the government's chief medical officer said.

U.N. Secretary-General Ban Ki-moon on Friday praised health care workers fighting the Ebola virus as he paid his first visit to Liberia and Sierra Leone following the outbreak.

Reuters