Officials have not confirmed the particular strain of Ebola causing the outbreak, which may have killed 20 people, but WHO's emergency response chief Peter Salama said it could be the Zaire, Sudan or Bundibugyo strain.
The new cases are in Mangina in the eastern Mabalako health zone, about 30 kilometers (18 miles) west of Beni, a city of more than 230,000 people.
The latest outbreak was found in the province of North Kivu, near the Congo's border with Uganda. The health ministry is investigating reports of viral hemorrhagic fever.
"Since we are coming out of another Ebola outbreak, we have kept staff and equipment in place", said Dr Matshidiso Moeti, WHO Regional Director for Africa.
Global experts set up a laboratory today in Beni, WHO and Congolese officials said.
The response to Congo's previous outbreak was considered a success despite the 33 deaths, as the use of a vaccine made by Merck helped contain the virus. There is no evidence yet suggesting the two outbreaks in the Congo are linked.
Preliminary laboratory results have confirmed a new cluster of cases in the Mangina area near Beni, a densely populated town, about 2,500 km from the last flare-up.
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Health officials flew six blood samples to the capital of Kinshasa, where four tested positive for the Ebola virus.
Once present in humans, it causes haemorrhagic fever, vomiting and diarrhea and is spread through direct contact with body fluids.
This is the DRC's 10th outbreak of Ebola since 1976, when the virus was discovered near the eponymous river in the north.
He says it is crucial to gain access to the area as quickly as possible.He says having people and material in the country from the outbreak in Equateur is very helpful in tackling the outbreak.
About 1,000 civilians have been killed by armed groups and government soldiers around Beni since 2014, and the wider region of North Kivu holds over 1 million displaced people.
The province shares borders with Rwanda and Uganda with a great deal of cross-border movement due to the trade activities, which, World Health Organization warned, could increase the risk of possible spread of the virus.