The Ebola outbreak in the Democratic Republic of Congo (DRC) has worsened sharply, with authorities late on Saturday raising the death toll to 204 and the number of suspected cases to 867.

The latest figures mark a steep increase from the World Health Organization's previous update on Friday, which recorded 177 suspected deaths and about 750 suspected cases.

The WHO has since revised its risk assessment for the outbreak in DR Congo from "high" to "very high" at the national level, warning that the virus is spreading rapidly in conflict-hit eastern regions. The regional risk remains high, while the global risk is still considered low.

The outbreak, caused by the Bundibugyo strain of Ebola, was declared a public health emergency of international concern earlier this month after cases were confirmed in both DR Congo and neighboring Uganda.

Unlike some previous Ebola strains, there is currently no approved vaccine for the Bundibugyo strain of Ebola.

Health officials say the epidemic is centered in the conflict-ravaged eastern provinces of Ituri and South Kivu, where insecurity and mass displacement are complicating efforts to contain the virus.

DR Congo Health Minister Samuel Roger Kamba said response teams were struggling to fully operate in areas affected by violence.

"We cannot properly deploy the response in areas that are not controlled, that are not secure," Kamba said, adding that humanitarian assistance alone was not enough without medical teams and laboratory support on the ground.

He said delays in detecting the Bundibugyo strain in Bunia forced officials to send samples to the capital Kinshasa for confirmation, delaying emergency interventions. Ongoing conflict and population displacement were also worsening the situation.

"There is a significant impact, especially since there are also displaced people, and this makes things even more complicated," Kamba said.

Concerns over the outbreak widened on Saturday after Uganda confirmed three new Ebola cases linked to DR Congo, bringing the total number of confirmed infections in the East African country to five. One person has died in Uganda so far.

Uganda's health ministry identified the new cases as a Ugandan truck driver, a Ugandan health worker and a Congolese woman. All three patients are alive and receiving treatment.

Cross-border transmission has raised fears of a wider regional outbreak. Africa CDC chief Jean Kaseya warned on Saturday that 10 African countries were at risk of being affected by the outbreak, citing high population mobility and insecurity in the region.

The countries identified as at risk are Angola, Burundi, the Central African Republic, the Republic of Congo, Ethiopia, Kenya, Rwanda, South Sudan, Tanzania and Zambia.

Africa CDC said $319 million was urgently needed to support response efforts in affected and high-risk countries, with more than 75% of the funding needed for DR Congo and Uganda alone.

Kaseya said more than $200 million had been pledged, but warned that much of the funding had yet to be mobilized.