Testing has confirmed that an initially unidentified illness that killed more than 50 people in northwest Democratic Republic of Congo was malaria, the country's National Public Health Institute (INSP) said late on Monday.

At least 943 people fell sick and 52 died in Equateur province at the start of the year, with symptoms ranging from fever and fatigue to vomiting and weight loss.

Health officials said in February that the condition was suspected to be either malaria or food poisoning.

Lab testing on samples has now confirmed that it was malaria, INSP coordinator Christian Ngandu said by telephone.

The research centre was still waiting for the results of water, drinks and food samples sent abroad to test for intoxication, he added.

A separate outbreak of disease in December, initially of unknown cause, was ultimately also identified as malaria.