A new Ebola case has been recorded in an area controlled by AFC/M23 rebels in eastern Congo, the group said, more than two months after it declared the outbreak over in the territory it holds.

The Rwanda-backed AFC/M23 rebels, who control large parts of North and South Kivu provinces after staging a lightning offensive last year, declared areas under their control Ebola-free in late June, after 21 days without new cases.

The latest case was detected in the Kayna health zone in North Kivu, near Lubero, the rebels said in a statement on Thursday.

The patient, a 21-year-old man, arrived from Butembo, a city in government-held territory, the statement said. It was not clear where he had contracted the virus.

He was identified as a suspected Ebola case at a health checkpoint on Wednesday and transferred to a quarantine facility, where tests confirmed infection the following day, the rebels said.

Health authorities said they had begun tracing contacts and stepped up surveillance to prevent further spread of the virus.

Rebel-held areas had recorded only four Ebola cases since the outbreak was declared in mid-May.

AFC/M23 officials had highlighted their handling of the outbreak as evidence of their ability to govern. Rwanda denies backing the rebels.