The WHO and the African Union's public health agency launched a $518-million joint plan on Friday to tackle the Ebola outbreak causing alarm in the Democratic Republic of Congo and its neighbours.

The World Health Organization and the Africa Centres for Disease Control and Prevention said the plan would last from June to November.

The outbreak was declared on May 15 in northeastern DRC, but the rare Bundibugyo strain of the Ebola virus is believed to have been spreading under the radar for some time beforehand.

According to the WHO's latest figures, there have been 381 confirmed cases in the DRC, including 64 deaths.

The outbreak in northeastern DRC has hit three provinces, with the epicentre in Ituri, which the Africa CDC says accounts for 90 percent of confirmed cases and 76 percent of deaths.

Across the northeastern border in Uganda, there have been 16 confirmed cases, including one death.

"The plan focuses on core areas: emergency coordination, surveillance, laboratory testing, infection prevention and control, clinical care, and community engagement," WHO chief Tedros Adhanom Ghebreyesus told a press conference.

"This is a practical plan. It sets out what we need to do now, together, to contain the current outbreak and reduce the risk of further spread.

"It's a time-bound plan, covering June to November this year," he said, adding that "it's a costed plan, at $518 million".

The current outbreak is bigger than the two previous recorded outbreaks of the Bundibugyo strain, in 2007 and 2012, according to the Africa CDC.

There are no approved vaccines or treatments for the Bundibugyo strain.