More than 1,000 people have now died of Ebola in the Democratic Republic of Congo, authorities said, as aid workers warned that the highly contagious virus combined with insecurity in the restive region was creating a "deeply worrying situation".
The current outbreak is the second deadliest on record, after an epidemic killed more than 11,300 people in West Africa in 2014-2016.
Efforts to roll back the outbreak of the haemorrhagic fever have been hampered by fighting but also by resistance within communities to preventative measures, care facilities and safe burials.
"In total, there have been 1,008 deaths (942 confirmed and 66 probable)," the health ministry said in a daily update late Friday.
The central African country declared a 10th outbreak of Ebola in 40 years last August centred in the city of Beni in North Kivu province before the virus spread into the neighbouring Ituri region.
The World Health Organization had initially voiced hope it would be able to contain the outbreak, thanks in part to a new vaccine.
But in recent weeks senior WHO officials have conceded that insecurity, scarce financial resources and local politicians turning people against health workers had seriously undermined the containment effort.
"We are dealing with a difficult and volatile situation," Michael Ryan, the executive director of WHO's Health Emergencies Programme, told reporters in Geneva on Friday.
"We are anticipating a scenario of continued, intense transmission," he added.
The long-standing presence of various rebel groups in Ituri and North Kivu has made it difficult for health workers to access those who might have come into contact with Ebola, a figure that currently stands at 12,000 people.
But beyond the militias, communities in the aftermath of DRC's December elections "are being manipulated" against cooperating with Ebola responders, Ryan said.
"Communities... need to be assured that all parties are supporting the public health response and that Ebola should not become further politicised in the process," he added.
Ryan said the UN health agency currently has enough vaccine stocks to meet its needs but doses may run short.
"We don't necessarily know which way this outbreak is going," he said.
More than 110,000 people have been vaccinated since the outbreak began. Neighbouring Rwanda and Uganda have also been vaccinating health workers.
- 'Deeply worrying' -
Humanitarian groups meanwhile warned Friday of health risks faced by tens of thousands of people uprooted by the resurgence of violence in the east of the country.
Among them, some 7,000 displaced people are housed in a primary school where the only water source is a nearby river and there are not enough toilets, 18 non-governmental organisations said in a statement.
In such conditions, the "risk of disease spread is high", they added.
"This is a deeply worrying situation. These people fear going back to their homes and are being forced to live in cramped, unsanitary conditions in an area where Ebola remains a significant threat," said Tamba Emmanuel Danmbi-saa from Oxfam, one of the groups that signed the document.
"These people urgently need food and adequate sanitation facilities as well as clean water and health services."
The groups said violence in the region, with rival rebel groups competing for resources and power, made it very difficult for humanitarian aid to reach those who need it, with some 60,000 people displaced in April alone.
Many of them, added the NGOs, find themselves trapped between the Ugandan border to the east, a region in their own country plagued by violence, and another nearby that is riddled with Ebola.
"As a result, some displaced people are being left with little choice but to return to the villages they fled, where they are at risk of further attacks.
"Others are avoiding official border points and choosing to cross illegally through the forests along the border or by boat across Lake Albert. This also increases the risk of Ebola being spread, since people are not being screened as they would be at the official border crossings."
In the conflict-ridden country as a whole, more than 13 million people need humanitarian aid, the NGOs said.
More than five million have had to flee their homes, and Uganda is already home to more than 1.2 million refugees.