The United Nations vowed Saturday to play a "strong role" in helping Liberia and its neighbours fight a deadly outbreak of Ebola in west Africa, which it said could take months to bring it under control.

Liberia has been particularly hard hit by the epidemic that has swept relentlessly across the region since March, accounting for almost half of the 1,427 deaths.

In recognition of the deteriorating situation, neighbouring Ivory Coast announced it had closed its borders with Liberia and Guinea in a bid to protect its citizens.

"Ebola in Liberia must be addressed to ensure a stable economy, future and society," said Karin Landgren, UN Secretary-General Ban Ki-Moon's special representative for the country.

"The magnitude of this outbreak requires a higher level of coordination than previous responses and the UN Mission in Liberia will play a strong role in this effort."

Her comments were echoed by David Nabarro, the UN's new pointman on Ebola, who arrived in the region on Thursday to tour the Ebola-hit countries of Liberia, Sierra Leone, Guinea and Nigeria.

Nabarro, a British physician tasked with coordinating the global response to the worst-ever outbreak of the deadly virus, said the UN would "ensure that adequate resources are given to sectors that need it most".

A day earlier, the World Health Organization (WHO) warned it could take "several months" to bring the epidemic under control.

"This is not something to turn around overnight, it is not going to be easy; we expect several months of hard work," said the UN agency's Assistant Director-General Keiji Fukuda, who is accompanying Nabarro on his tour.

- Death toll rises -

Their visit has coincided with a surge in new cases of Ebola in the region, as affected countries struggle to contain the spread of the killer virus.

The WHO said Friday that the death toll had risen to 1,427 out of more than 2,600 cases -- with 77 succumbing to the disease between August 18 and 20.

A British national who lives in Sierra Leone has tested positive for Ebola, the first British citizen to have contracted the disease, according to officials.

Britain's Mail on Sunday newspaper reported that the infected man was a medic working for a charity in Sierra Leone.

He was reportedly set to be flown back to Britain for treatment in the next couple of days. The Department of Health did not immediately respond to a request to confirm the report.

Nigeria, which has seen progress in battling the outbreak, has suffered five deaths to date. Officials said Friday that two more people had tested positive for Ebola.

Liberia remains the worst-affected country with 624 deaths. Guinea has seen 406 people die while in Sierra Leone, 392 have succumbed to the haemorrhagic fever.

Aid workers said crematoriums in the Liberian capital Monrovia were struggling to deal with dozens of bodies arriving every day, and earlier this week, violence erupted in an Ebola quarantine zone in the capital after soldiers opened fire on protesting crowds.

The failure of West African countries to bring the epidemic under control has worried its neighbours and nations further afield.

Many flights to the region have been cancelled, and authorities around the world have adopted measures to screen travellers arriving from affected nations.

A Canadian hospital said it had placed a patient who recently returned from Guinea in isolation as it awaits whether the individual tests positive for Ebola.

The patient was quarantined after experiencing a high fever, according to Montreal's Maisonneuve-Rosemont Hospital.

And in Bolivia, authorities said they were investigating a first potential case of Ebola after a patient, who is being treated for a fever, diarrhoea and vomiting, had made stopovers in several African cities.

The Ivory Coast closed its borders with Guinea and Liberia just days after Senegal did the same with Guinea, where the outbreak is thought to have begun.

It came in the wake of the first reported Ebola deaths in the southeast of Liberia, which borders the Ivory Coast.

Meanwhile, an official said Cameroon has suspended imports of meat and animals "sensitive" to the Ebola virus.

- 'Pariah states' -

The extreme measures taken against affected countries, especially by their neighbours, have caused friction in the region.

Ibrahim Ben Kargbo, the chairman of Sierra Leone's presidential task force on Ebola, said he was "surprised" by the lack of solidarity among African countries.

It "gives the impression that we are pariah states," Kargo said on state television, in reference to a South African ban on non-citizens travelling from Sierra Leone, Guinea and Liberia.

"The epidemic is not manmade but a natural phenomenon, we did not create it," said Kargbo, who is a presidential advisor and former information minister.

"Once we get over the epidemic, we will begin to look at ourselves to know who our friends are."

No cure or vaccine is currently available for the deadly virus, which is spread by close contact with body fluids, meaning patients must be isolated.

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