More than 50 refugees fleeing fighting in eastern Democratic Republic of Congo have died in neighbouring Burundi, the United Nations Refugee Agency told Reuters late on Friday.

Of a total 53 deaths recorded, 25 people died due to a cholera outbreak, the agency said, while six others died from anemia and other complications related to malnutrition, it said.

The UN said it was working with the health ministry and other partners to investigate the cause of the other deaths.

More than 100,000 Congolese have sought refuge in Burundi since fighting near the border intensified in early December and rebels seized the town of Uvira, the UNHCR said.

Jean Jacques Purusi, governor of South Kivu province where Uvira is located, described the situation in Burundi as "misery" and "a crisis completely forgotten by the international community and media."

Congo's state and social affairs ministry said it was leading a humanitarian mission to help displaced Congolese in Burundi, providing food, medicines, and non-food items.

A spokesperson for Burundi's National Office of Protection of Refugees and Stateless Persons did not answer calls or respond to a texted request for comment.