Aid group Doctors Without Borders said fighters in South Sudan have destroyed and looted hospitals in what it calls "disturbing" incidents against medical facilities, staff and patients since conflict broke out there in December.
In a statement released Wednesday, the group said its teams found at least 14 dead bodies at a hospital Saturday in Malakal, and that several bodies showed signs that the patients had been shot in their beds.
Malakal is the capital of Upper Nile state and has been the site of some fierce fighting between government troops and rebels. The two sides clashed there last week, despite signing a cessation-of-hostilities deal in Ethiopia last month.
United Nations humanitarian official Toby Lanzer called the situation in Upper Nile "very unstable" as he traveled there for a visit Wednesday.
Doctors Without Borders said the hospital in Malakal had been looted and many of its wards burned.
In nearby Unity State, the group said its staff found a "horrific scene" at Leer Hospital, where buildings and equipment were burned, while drugs, patient beds and other supplies were looted.
The head of the group's mission in South Sudan, Raphael Gorgeu, said hospitals have become "targets of attack and brutality" and that the violence shows a lack of respect for medical care.
Fighting in South Sudan has killed thousands of people since mid-December.
The United Nations humanitarian office said an estimated 880,000 people have been forced from their homes, including 171,000 who have fled to other countries.
The U.N. says aid groups need about $1.3 billion by June to help more than 3 million people affected by the crisis, and that so far donors have given 20 percent of that total.