The World Health Organization voiced concern Tuesday over the “scale and speed” of an Ebola outbreak in the Democratic Republic of the Congo that has killed an estimated 131 people.

The WHO has declared the surge of the highly contagious haemorrhagic fever an international health emergency and called an emergency meeting on the crisis Tuesday.

No vaccine or therapeutic treatment exists for the Bundibugyo strain of Ebola responsible for the latest outbreak of the disease, which has killed more than 15,000 people in Africa in the past half-century.

With the new outbreak largely concentrated in difficult-to-access areas hit by long-running conflicts, few samples have been laboratory-tested and figures are based mostly on suspected cases.

"We have recorded roughly 131 deaths in total and we have around 513 suspected cases," Congolese Health Minister Samuel Roger Kamba said on national television early Tuesday.