Ebola outbreak in remote part of DR Congo
In a television address, Health Minister Oly Ilunga confirmed the cases while urging the population "not to panic".
The country "has taken all necessary measures to respond quickly and efficiently to this new outbreak", he said.
The DR Congo outbreak is the first there in three years. The three deaths all occurred since April 22.
The WHO said it was working closely with DR Congo authorities to help deploy health workers and protective equipment in the remote area, which is difficult for teams to access, in order to "rapidly control the outbreak".
The organisation underlined the importance of tracing people who had contact with confirmed victims to prevent the disease spreading.
Sufferers are advised to keep themselves isolated while awaiting treatment for a disease whose incubation period is 21 days.
The WHO said the outbreak, the eighth to date in DR Congo, had affected an equatorial forest region difficult to access in Bas-Uele province, bordering Central African Republic.
The last instance of Ebola in Congo in 2014, which was not linked to an outbreak in neighbouring states at the time, was quickly contained and killed 49 people according to official figures.
That outbreak saw 66 registered cases hit the district of Boende some 800 kilometres (500 miles) northeast of Kinshasa for an official fatality rate of 74.2 percent.
The United Nations at the time saluted the "immense work" DR Congo authorities had put in to contain the disease spread.
In 2013, an Ebola crisis began in Guinea, Sierra Leone and Liberia.
Liberia was the last of those states to be declared clear in January 2016. Congo's outbreaks have all been in areas not linked to the West African cases.
The WHO was criticised at the time for responding too slowly and failing to grasp the gravity of the latest outbreak of a disease first recorded in DR Congo in 1976.
Last week, the WHO said almost 12,000 people had participated in a ground-breaking vaccine trial the agency organised in Guinean capital Conakry through to January last year.
Final results from the trial published in The Lancet released last December showed the experimental vaccine offered protection against the virus and would help to bolster an early response to future outbreaks.
The WHO led the trial with Guinea's ministry of health, Medecins sans Frontieres and the Norwegian Institute of Public Health, in conjunction with other international partners.
The vaccine is now awaiting formal licensing clearance.
Ebola is a viral illness whose initial symptoms may include a sudden fever, aching muscles and a sore throat, with subsequent symptoms including diarrhoea and vomiting and, on occasion, internal and external bleeding.
Humans can catch the illness from close contact with infected animals.
Inter-human transmission can then occur through direct contact with infected blood or bodily fluids. Mourners can also catch it if they have direct contact with the bodies of victims at funerals.
The WHO said specialist teams were headed for the area and hoped to arrive within 48 hours.
It said the health zone at Likati some 1,300 km from Kinshasa was very difficult to access but stressed it was crucial to pinpoint who had had contact with those affected in order to nip the latest outbreak in the bud.
"RDC has very experienced human resources to do this," the WHO noted in calling on partner organisations to rally and provide a "coordinated and appropriate" response.
The Alliance For International Medical Action said in a statement one of its teams was on its way to Likati with protective gear and medicine to treat "suspected and confirmed cases."
© 2017 AFP