The nearly 90,000 refugees who fled to Burundi after the recent escalation of violence in eastern Democratic Republic of Congo face dire conditions in cramped camps with limited access to food and water, aid agencies say.
Congolese M23 rebels recently captured the city of Uvira, near the Burundi border, and the fighting forced hundreds of thousands from their homes. The rebels say they have since withdrawn.
Medical charity MSF, which has been providing emergency help, has raised concerns about the worsening humanitarian situation.
The UN's refugee agency, UNCHR, said those especially affected are children and women - including pregnant women - some who reported going without food for days.
MSF said it had been treating an average of 200 people daily since the refugees started arriving in Burundi in the last two weeks.
We see people in a state of distress, despair, and exhaustion. We see women who gave birth while fleeing, some that give birth in our clinic, said Zakari Moluh, the MSF project coordinator describing the situation in Ndava, north-west Burundi.
The charity has warned of the risk of the spread of epidemic diseases such as cholera and measles, and a catastrophic increase of malaria cases among vulnerable people.
Meanwhile, the UN's World Food Programme (WFP) says it is increasing its life-saving aid to over 210,000 of the most vulnerable people displaced by the DR Congo violence.
It notes that about half a million people have been forced from their homes in South Kivu province since the beginning of December.
The WFP says it is supporting 71,000 new Congolese arrivals to Burundi with hot meals in transit centers.
It adds that services across the province are on the brink of collapse, as health centres have been looted, medicines are unavailable, and schools remain closed. The agency has called for urgent funding to be able to continue providing food aid in the next three months.
The capture of Uvira at the beginning of the month extended the M23's territorial gains in eastern DR Congo after they had earlier captured the major cities of Goma and Bukavu.
The rebels said they would pull out of Uvira last week under pressure from the US, but their reported withdrawal has been disputed by Congolese authorities.
The US brokered a peace deal between the Congolese and Rwandan governments aimed at ending the long-running conflict in DR Congo. The US accuses Rwanda of backing the M23 rebels, which it denies.
The rebels were not signatories to that peace deal, but they have been part of a parallel peace process led by Qatar, a US ally that has strong ties with Rwanda.
