NAIROBI, Kenya — An Ebola outbreak has been declared in northern Democratic Republic of Congo and has killed at least three people in the past three weeks, the World Health Organization said on Friday.

The affected zone is in a forested area of Lower Uele Province, and it is close to the border with the Central African Republic, the W.H.O. said.

The outbreak is not linked to previous Ebola flare-ups in Congo, nor the one that tore through West Africa in 2014, killing more than 11,000 people, said Tarik Jasarevic, a W.H.O. spokesman. That outbreak was significant because it reached major cities and began in a part of Africa that had never seen Ebola before.

Mr. Jasarevic said that there had been a number of Ebola outbreaks in the Lower Uele region since 2000. Congo has had eight outbreaks of Ebola since 1976, according to the W.H.O.

The virus circulates in bats and sometimes causes outbreaks in primates. Scientists believe that humans usually contract it directly from bat guano, from eating bats or from eating primates that have died of Ebola.

Ebola can persist for months in certain body tissues that are relatively protected from the immune system, including the eyes and the testes, and little is known about the long-term effects of the virus.

Of the five blood samples taken from the newest suspected cases and analyzed by the Congolese National Institute of Biomedical Research, one tested positive for Ebola, according to the Health Ministry. Since April 22, the ministry has recorded nine suspected cases and three deaths.

Dr. Armand Sprecher, a public health specialist and Ebola expert who works with Doctors Without Borders — widely known by its French name, Médecins Sans Frontières — said by telephone from Brussels that unless a full investigation were conducted, it would be hard to know how severe the new outbreak could be.

“It’s too early to say,” Dr. Sprecher said. “It could just be that one case, which is unlikely, or that there are more cases, but that have not been reported.”