Health Minister Eteni Longondo said four people who died in Mbandaka were confirmed as positive cases following testing at the national biomedical laboratory in the capital Kinshasa.
"We have a new Ebola epidemic in Mbandaka," Longondo told reporters. "We are going to very quickly send them the vaccine and medicine."
The outbreak was confirmed by World Health Organization Director-General Tedros Adhanom Ghebreyesus, who tweeted: "This outbreak is a reminder that #COVID19 is not the only health threat people face."
Congo has been struggling to put an end to a nearly two-year-old Ebola outbreak near its eastern borders with Rwanda and Uganda, which has killed more than 2,200 people, the world's second-deadliest outbreak of the disease on record.
It was days away in April from declaring the end of that outbreak, its tenth since the virus was discovered in 1976, when a new chain of infection was confirmed in the east. However, no new cases have been detected there in over 30 days.
(Reporting by Benoit Nyemba and Stanis Bujakera Writing by Alessandra Prentice Editing by Aaron Ross and Giles Elgood)
epa07802957 Protective equipments are hung to dry at an Ebola transit center in Beni, North Kivu province, Democratic Republic of the Congo, 29 August 2019. The death toll from the DR Congo's Ebola epidemic, an outbreak declared a global health emergency by the World Health Organisation (WHO), is expected to pass two thousand soon. EPA-EFE/HUGH KINSELLA CUNNINGHAM 