Congo has begun Ebola vaccinations of medical staff in the northwest city of Mbandaka, a Reuters witness said, the first in the Central African country to help stem an outbreak believed to have killed 25 people since early April.

The WHO is sending over 7,540 doses of Ebola vaccine to Congo, 540 of which have been earmarked for Mbandaka where four Ebola cases have been confirmed.

Health workers in DRC began the vaccination aimed at containing an outbreak of the deadly Ebola virus.

A spokesperson for the health ministry,  Jessica Ilunga said that 4,000 doses of vaccine were shipped on Saturday to the city of Mbandaka.

The outbreak is Congo’s ninth since the disease made its first known appearance in the 1970s.

The cases in Mbandaka, a port city on the Congo river, have raised concerns that the virus could spread downstream to the capital Kinshasa, which has a population of 10 million.

A government spokesman said that Congo’s partners had promised to make available a total of 300,000 doses of vaccine.