Geneva (AFP) - The deaths of 57 more people from Ebola in west Africa have pushed the overall fatality toll from the epidemic to 729, the World Health Organization said Thursday.

The 57 deaths were recorded between Thursday and Sunday last week in Guinea, Liberia, Nigeria and Sierra Leone, the UN health agency said in a statement.

It said 122 new cases were detected over those four days, taking the total number of confirmed and likely infected cases from the outbreak so far to 1,323.

WHO said the trend in Guinea, Liberia and Sierra Leone "remains precarious with ongoing... transmission of infection".

Guinea is suffering the worst from the disease, which causes often fatal bleeding and has no vaccine. The country's authorities reported 20 more deaths apparently from Ebola in the last four days of last week, taking its national fatility figure to 339.

Liberia saw 27 more deaths, for a total national death toll of 156.

Sierra Leone reported nine more deaths for a total 233 dead.

Nigeria, Africa's most populous country, reported its first death from Ebola in that period.

WHO said the medical sample taken from the patient who died in Nigeria shortly after arriving by air had still not been analysed by its regional lab because courier companies were refusing to transport it.

The UN agency added that it "does not recommend any travel or trade restrictions" be applied to Guinea, Liberia, Nigeria, or Sierra Leone at this time.

The WHO's statement was available at: http://www.who.int/csr/don/2014_07_31_ebola/en/.