In a press conference on Friday, the WHO said the Ebola epidemic required an extraordinary response to stop its spread.

"Countries affected to date simply do not have the capacity to manage an outbreak of this size and complexity on their own," said WHO Director General Dr. Margaret Chan. She called on the international community to provide urgent support to countries affected by the crippling virus.

The WHO previously declared similar emergencies for polio in May, and for the swine flu pandemic in 2009.

The agency had convened an expert committee this week for an emergency session to assess the severity of the ongoing Ebola epidemic in West Africa. The virus was first identified in Guinea in March, before it spread to Sierra Leone and Liberia.

All three countries have already implemented states of emergency.

Deadliest outbreak on record

The WHO has described the current outbreak as unprecedented. So far, it has killed 932 people and infected more than 1,700, with the death rate hovering around 50 percent.

Medical charity Doctors Without Borders has warned that the virus is "out of control," while US health authorities acknowledges on Thursday that the pathogen's spread outside Africa was inevitable.

The first European Ebola victim, Spanish Roman Catholic priest, Miguel Pajares, was flown out of Liberia on Thursday. Authorities said the 75-year-old's condition was stable. Meanwhile two Americans who are being treated in Atlanta, Georgia, after being infected in Liberia are showing signs of improvement.

Ebola was first discovered in 1976 in what is now the Democratic Republic of Congo. The virus causes severe fever, headaches, vomiting and bleeding, and is spread via bodily fluids.

nm/rc (Reuters, AFP, AP)