The UN agency announced the plan on Thursday in response to the "unprecedented" Ebola outbreak in West Africa that has killed 729 people and infected 1,323 since February.

WHO Director Margaret Chan will meet the presidents of the affected countries in Conakry, Guinea on Friday, the organization said in a statement.

"The scale of the Ebola outbreak, and the persistent threat it poses, requires WHO and Guinea, Liberia and Sierra Leone to take the response to a new level and this will require increased resources, in-country medical expertise, regional preparedness and coordination," said Chan.

Emergency plan

The response identifies the need for "several hundred more personnel" to be deployed to affected regions in order to ease the strain on medical facilities, the WHO said, appealing to donor countries for clinical doctors and nurses, epidemiologists and logisticians.

It aims to stop the transmission of Ebola by boosting disease surveillance, particularly in border areas, protecting health workers from infection and doing a better job of informing communities about the virus.

"The plan sets out new needs to respond to the outbreak across the countries and bring up the level of preparedness in neighboring countries," said WHO spokesman Paul Garwood. "They need better information and infection-control measures."

Travel warning

The severity of the epidemic prompted the US government on Thursday to issue travel warnings to Guinea, Liberia and Sierra Leone.

Centers for Disease Control and Prevention (CDC) Director Tom Frieden said the outbreak "represents a potential risk to travelers."

The CDC is also sending 50 extra specialists to affected areas, he added.

Sierra Leone declared a state of emergency Thursday and called on troops to quarantine Ebola victims, joining neighbor Liberia in implementing strict government controls.

Ebola can be fatal in up to 90 percent of cases, though the current outbreak has killed around 60 percent of those infected.

dr/rc (Reuters, AFP, AP, dpa)