The World Health Organisation obtained 4,000 doses of an experimental Ebola vaccine and was preparing for deployment in Congo, its Africa director, Matshidiso Moeti, told Reuters by telephone on Sunday.
The declaration followed laboratory results that confirmed two cases of the disease.
World Health Organization said Thursday that between April 4 and May 5, twenty-seven cases of fever with hemorrhagic signs, including 17 deaths, were reported in the DRC's Bikoro district.
Ebola is a highly infectious disease spread through contact with even small amounts of bodily fluid of an infected person.
President Joseph Kabila also met WHO Director-General Tedros Adhanom Ghebreyesus in Kinshasa on Sunday.
They said the Congolese government has reacted quickly to the crisis, but expressed concern about Bikoro's proximity to the provincial capital Mbandaka, a city of about one million people.
Officials are racing to prevent the virus from spreading out of control, as happened in West Africa from 2014 to 2016, when Ebola killed more than 11,300 people in Guinea, Sierra Leone and Liberia. It is a hemorrhagic fever, marked by spontaneous bleeding from internal organs and, in most cases, death.
At present the outbreak did not meet the criteria for declaring a "public health event of global concern", which would trigger the formation of an emergency WHO committee.
The worst-ever Ebola outbreak started in December 2013 in southern Guinea before spreading to two neighbouring west African countries, Liberia and Sierra Leone, killing more than 11,300 people out of almost 29,000 registered cases.
The DRC is now in its ninth Ebola outbreak since 1976.