DAKAR (Reuters) - The death toll from an outbreak of Ebola in Guinea, Liberia and Sierra Leone has hit 337 since February, the U.N. World Health Organisation said on Wednesday, as weak local health services struggle to contain the highly contagious disease.

WHO said 47 new cases and 14 deaths had been reported in the region in the last week alone, despite the dispatch of international experts to help out.

Guinea remains worst affected, with 264 Ebola-related deaths, the WHO data showed, but the toll in Sierra Leone and Liberia has recently spiked, hitting 49 and 24 respectively.

WHO has tried to coordinate the regional response but imposing the restrictions needed to control such an infectious disease has proven difficult. WHO said last month an earlier dip in cases masked the seriousness of the outbreak. [ID:nL6N0OE5EQ]

Guinea's new cases were reported in Gueckedou, a remote southeast region where the outbreak was first confirmed, but also in Boffa, hundreds of kilometres (miles) to the northwest of the capital city Conakry.

Liberia reported four deaths in its capital Monrovia on Tuesday, the first to be confirmed in the sprawling ramshackle seaside city. [ID:nL5N0OY3Q1]

Sierra Leone's toll has risen rapidly since it confirmed its first deaths in late May.

The outbreak has led to some restrictions on flights and trade in the region but international mining firms operating in the three countries say operations have not yet been affected.

Discovered in 1976 after an outbreak in the Democratic Republic of Congo, Ebola has a fatality rate of up to 90 percent and there is no vaccine and no known cure.

The virus initially causes raging fever, headaches, muscle pain, conjunctivitis and weakness, before moving into more severe phases of causing vomiting, diarrhoea and haemorrhages.