A hygienist decontaminates a doctor's boots as they leave the patient care unit of a treatment center in Bunia, Ituri, in eastern Democratic Republic of Congo, on Monday. BENEDICTION MURHABAZI/AFP

The Ebola outbreak in the Democratic Republic of Congo is spreading faster than previously understood, with the United Nations warning that the epidemic could be at least two to four times larger than official figures and is recording some of the highest daily infection numbers since it began two months ago.

With nearly 2,000 confirmed cases and more than 700 deaths across five provinces as of July 11, health officials said the outbreak has become the third-largest Ebola epidemic ever recorded and the fastest-growing in recent history.

"We've seen the fastest growth in a single month since the outbreak started and of all the Ebola outbreaks that we have managed," Chikwe Ihekweazu, executive director of the WHO Health Emergencies Programme, told reporters in Geneva after returning from Bunia in eastern DR Congo, the epicenter of the outbreak, according to a UN statement on Tuesday.

"Over the last few days, we've seen some of the highest numbers of new infections in a single day," he said, noting that more than 80 cases were confirmed within a 24-hour period in recent days, among the highest daily increases recorded since the outbreak began.