WHO said today that among the 20 suspected cases, two now have tested positive for the virus.
Ebola was blamed for more than 11,000 deaths in West Africa during 2013-2016. Congo has already experienced seven much smaller outbreaks.
So far three people have died in Congo's Bas-Uele province, an area more than 800 miles (1,300 kilometers) from the capital, Kinshasa.
There is no specific treatment for Ebola, which is spread through the bodily fluids of people exhibiting symptoms. A new experimental vaccine has been shown to be highly effective against the virus, though quantities are currently limited.