"The security has become a major impediment", said Michael Ryan, executive director of the WHO's Health Emergencies Programme, earlier in the day.
The failure to overcome the outbreak so far has seen it evolve into the second-deadliest in recorded history, trailing an epidemic between 2013-2016 that killed about 11,300 people in West Africa as it surged through Guinea, Sierra Leone and Liberia.
Health Minister Oly Ilunga said that four deaths in the outbreak's epicentre of Katwa pushed the death toll to 1,008.
Worryingly, many of these deaths are occurring within communities which means that people are not seeking care and treatment in health centres.
Ebola broke out in North Kivu in August 2018 and spread to neighbouring province, Ituri.
The long-standing presence of various rebel groups in Ituri and North Kivu has made it hard for health workers to access those who might have come into contact with Ebola, a figure that now stands at 12 000 people.
On Tuesday, the World Health Organization said support to control the Ebola outbreak has lagged and maintaining security in the conflict-prone area has been hard.
The Merck vaccine will still be used in "ring vaccination" of people exposed to the virus and their contacts, Ryan said, but the World Health Organization is also studying use of a single dose to stretch supplies, an option experts would review on Monday.
Many people fear going to Ebola treatment centers, choosing instead to stay at home and risk transmitting the disease from the virus to caretakers and neighbors. Vaccination campaigns also have slowed in areas too volatile for health personnel to visit.
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.