File photo: Health workers are seen inside the "red zone" of an Ebola treatment centre in Butembo in North Kivu province, Congo. AFP
The Rwanda-backed M23 and Rwandan troops took the North Kivu provincial capital Goma last week and are now pushing into neighbouring South Kivu province.
Thousands have died and huge numbers have had to flee the violence as the force has overtaken swathes of the mineral-rich region.
They have routed DR Congo troops and their allies in what is just the latest episode of decades-long turmoil in eastern DRC.
The International Committee of the Red Cross had voiced fears late last month over the risk that fighting in Goma could allow samples of Ebola, Marburg, mpox and other pathogens to escape from an important lab in the city.
But the World Health Organization said Friday the situation was under control.
"I can say the lab is safe," Boureima Hama Sambo, WHO's representative for the Democratic Republic of Congo, told reporters in Geneva, speaking from Kinshasa.
"The bio bank of this lab is very well kept," he said.
The UN health agency had managed "to supply fuel for the generator to keep running even when electricity was cut", he added.
The WHO, working closely with the Red Cross, had also ensured that food and water were brought in to the people guarding the facility to ensure "nothing has been attempted" in terms of breaching the lab.
In particular, he highlighted that the lab could be "remotely locked, and this is what has been done".
Now, he said, "the lab is functioning normally and there's no threat coming out of this lab for the moment.
"There's no concern for now that any pathogen can be leaked out."
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