The United Nations appealed for $33 million in urgent funding to help more than 80,000 people who have fled to Burundi after the latest advance by Rwanda-backed militants in the eastern Democratic Republic of Congo.
After seizing the major Congolese cities of Goma in January and Bukavu in February, the M23 armed group launched a new offensive in early December near the Burundian border, even as Rwanda and the DRC signed a peace agreement in Washington.
The M23 on December 10 took control of Uvira, a city of hundreds of thousands of inhabitants, giving it control of the land border with the DRC's ally Burundi.
Under US pressure, the group said it would withdraw from Uvira but some of its police and intelligence agents were still deployed in the city on Thursday, according to local and security sources.
"Following recent violent clashes in South Kivu, notably around Uvira... a significant influx of refugees has occurred since December 5, with an estimated arrival of nearly 80,000 people through various entry points," said the office of the UN High Commissioner for Refugees.
The refugees include 71,989 Congolese and 8,000 Burundians, it added.
The organisation, which expects a total of 90,000 new arrivals, launched an appeal on Thursday for $33.2 million (28.3 million euros) to enable it to host them in decent conditions.
It published a photo showing dozens of people camping under trees, without any infrastructure to accommodate them.
"Living conditions are very bad. We are in raining season here in Burundi, and without the necessary shelters... that is exposing people actually to even harsher conditions," said Brigitte Mukanga-eno, the UNHCR representative in Burundi, who described the situation as "overwhelming".
On Tuesday, two Burundian officials estimated that at least 85,000 people had fled the DRC in recent weeks to seek refuge in Burundi.
Ezechiel Nibigira, the Burundian president of the Economic Community of Central African States (ECCAS), reported 25,000 refugees in Gatumba, western Burundi, and nearly 40,000 in Buganda in the northwest, most of them "completely destitute".
The administrator of the southwestern Burundian city of Rumonge, Augustin Minani, described to AFP a "catastrophic" situation in his commune with 20,000 to 25,000 refugees from the DRC who "lack everything", of whom "the vast majority are dying of hunger".
Since the M23 began its latest offensive on December 2, the fighting has internally displaced 500,000 people in the DRC's South Kivu province alone, including 200,000 people within Uvira territory, according to the UN refugee agency.