China will send more medics to Ebola-hit Sierra Leone to help boost laboratory testing for the virus, raising the total number of Chinese medical experts there to 174, the UN said Tuesday.

"The most urgent immediate need in the Ebola response is for more medical staff," World Health Organization chief Margaret Chan said in a statement, hailing the Chinese commitment.

China has said it will dispatch a mobile laboratory team to Sierra Leone, where more than 500 people have died so far from Ebola.

It will send a 59-person team from the Chinese Centre for Disease Control, including epidemiologists, clinicians and nurses, WHO said.

"The newly announced team will join 115 Chinese medical staff on the ground in Sierra Leone virtually since the beginning," Chan said, stressing that the new commitment was "a huge boost, morally and operationally."

The Chinese contribution comes in response to WHO's urgent appeal to countries around the globe to step up their assistance to help bring the raging epidemic under control.

The worst-ever Ebola contagion has already killed more than 2,400 people in west Africa since it erupted earlier this year.

The announcement of China's contribution comes as US President Barack Obama was set Tuesday to announce US efforts to "turn the tide" in the Ebola epidemic.

Washington plans to order 3,000 US military personnel to west Africa, while US advisors will train up to 500 health care providers per week in Liberia -- the country hardest-hit by the epidemic.

The International Federation of Red Cross and Red Crescent Societies (IFRC) meanwhile announced late Monday that it had opened its first Ebola treatment centre in Kenema, one of the districts of Sierra Leone worst affected by the deadly outbreak.

The centre, which is staffed with 19 international workers and 80 national employees, will have room for 60 patients, IFRC said.

The first patients, including an 11-year-old girl from Freetown, were already being treated there, it added.

The tropical Ebola virus can fell its victims within days, causing severe fever and muscle pain, weakness, vomiting and diarrhoea -- in some cases shutting down organs and causing unstoppable bleeding.

No licenced vaccine or treatment exists but health experts are looking at fast-tracking two potential vaccines and eight treatments, including the drug ZMapp.