Democratic Republic of Congo on Thursday began vaccinating frontline health workers with a vaccine approved for a different Ebola species, as authorities seek to contain the country's largest and deadliest Ebola outbreak on record.

Health Minister Samuel-Roger Kamba said Congo had received more than 50 000 doses of the Ervebo vaccine and would begin vaccinations in provinces affected by the outbreak, prioritising health workers.

Ervebo is licensed against the Zaire species of Ebola and was used successfully in previous outbreaks. The current epidemic is caused by the Bundibugyo species, for which there is no approved vaccine or treatment.

Early animal studies suggest Ervebo could provide some protection against Bundibugyo, and authorities are using 20 000 of the 70 000 doses allocated to Congo in a clinical trial to assess its effectiveness in humans.

Several vaccines specifically targeting the Bundibugyo species are also under development, including candidates from the University of Oxford and the International AIDS Vaccine Initiative (IAVI).

Vaccinations began in the northeastern city of Kisangani, the capital of Tshopo province, one of six provinces affected by the outbreak.

Kamba said the campaign would first cover provinces surrounding Ituri, where the outbreak was first detected and remains most heavily concentrated, before progressively moving inward.

The outbreak, declared on May 15, has infected 5 794 people and killed 2 786, according to the latest government figures, making it the world's second deadliest Ebola epidemic on record.