More than 700 more Ebola cases have emerged in West Africa in the past week week, a statistic that showed the outbreak was rapidly accelerating, the World Health Organisation has said.

The UN health agency said on Thursday that more than 5,300 people have now contracted the virus, and that the latest statistics showed that just under half of these cases were recorded in the last three weeks.

Rain or shine, the shutdown exercise is going to go ahead. During the three days ... the job is going to get done.

Steven Gaojia,  head of emergency operation centre

Just three weeks ago the number of new cases was around 500 for a one-week period. 

The death toll also passed 2,600 people, an increase of roughly 200 from the last estimate, WHO said.

Later on Thursday, the UN Security Council declared the outbreak a "threat to international peace and security" and called on all states to provide urgent resources and assistance to help tackle the crisis.

The alarm came as Sierra Leone readied for an unprecedented three-day nationwide lockdown to contain the spread of the Ebola in a controversial move which experts claimed could worsen the epidemic.

The population of six million will be confined to their homes from midnight on Thursday as almost 30,000 volunteers go door-to-door uncovering patients and bodies hidden in people's homes.

"Rain or shine, the shutdown exercise is going to go ahead. During the three days ... the job is going to get done," said Steven Gaojia, head of the government's emergency operation centre.

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The worst-ever outbreak of Ebola has claimed more than 500 lives in Sierra Leone, one of three countries at the epicentre of the epidemic.

"Ose to Ose Ebola Tok" - "house-to-house Ebola talk" in the widely-spoken Krio language - will see more than 7,000 volunteer teams of four visiting the country's 1.5 million homes.

They will hand out bars of soap and information on how to prevent infection, as well as setting up "neighbourhood watch"-style community Ebola surveillance teams.

Soldiers to enforce

The government has said the teams will not enter people's homes and are not tasked with collecting patients or bodies, but will call emergency services or burial teams "if by chance the teams happen to bump into such situations".

Extra beds have been set up at schools and hospitals across the country, including 200 around Freetown, with the government projecting a 15 to 20 percent upsurge of cases as new patients are discovered.

Community activists and civil society leaders have been recruited to help thousands of police and soldiers enforce the curfew.

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Experts warned however that coercive measures to stem the epidemic, such as confining people to their homes, could backfire badly and would be extremely hard to implement effectively.

Jean-Herve Bradol, a former director of Doctors without Borders (MSF), said the goal seemed "highly unrealistic".

In separate development, the medical charity MSF on Thursday criticised the delay in repatriating a foreign health worker infected with Ebola in Africa after it took two days to fly out the infected French volunteer from Liberia.

"It's just too long when you see that it takes 42 hours from the moment when a case is detected to when they are repatriated," Brice de la Vigne, MSF operations director, said.

MSF is the leading organisation fighting Ebola, with more than 2,000 staff members working across West Africa. Its president, Joanne Liu, had previously warned that infection among its own staff could exacerbate the outbreak by spreading it further among the healthy.

The UN Security Council will convene on Thursday to decide if Ebola is deemed a global threat.

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Source: Agencies