Guinea has announced the closure of its borders with Sierra Leone and Liberia in a bid to halt the spread of Ebola, the virus that has killed nearly 1,000 people in the three West African countries this year.

At least 367 people have died in Guinea since March and 18 others are being treated in the country in isolation, but the decision was taken primarily to avoid infected people crossing into the state, authorities said.

"We have provisionally closed the frontier between Guinea and Sierra Leone because of all the news that we have received from there recently," Health Minister Ramy Lamah told a news conference on Saturday, adding that Guinea had also closed its border with Liberia.

The measures had been taken in consultation with the two neighbours, Moustapha Koutoub Sano, Guinea's Minister for International Co-operation, told the news conference. 

The UN World Health Organisation said on Friday that Ebola represents an international health emergency and could continue spreading for months.

Nigeria became the third African nation, after Sierra Leone and Liberia, to declare a national emergency on Friday as the region's healthcare systems struggle to cope with the advance of one of the world's deadliest diseases.

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Source: Al Jazeera and agencies