A total of 38 people have died since the disease was identified in May, but the WHO says there are currently no confirmed cases in the country.
Its regional emergency director, Dr Ibrahim Socé-Fall, told BBC Focus on Africa radio that it was too early to celebrate as the test results from four suspected cases were still not known.
He praised the rapid response by the Congolese authorities and other health agencies.
Dr Socé-Fall said more than 3,000 people were given an experimental vaccine and none of them had contracted the virus. ‘Progress’ in tackling Ebola in DR Congo.