(CNN) -- Hundreds of aid workers and patients scuttled into the wilderness to escape escalating violence in South Sudan, a medical charity said.
Doctors Without Borders, also known as Medecins Sans Frontieres, said its 30 staff members in Unity State went into hiding Friday, taking the most severely-injured patients from a local hospital along.
"Other patients who were well enough to leave on their own accord also fled," the organization said. "There are no longer any patients or staff left."
Its workers were among about 240 people who took to the bush, it said.
"In the past three days, the situation became too unstable and the only way to provide medical care was to take patients out of the hospital and to flee with the population into the bush," said Raphael Gorgeu, head of mission for MSF.
"MSF is extremely worried for the safety and wellbeing of its staff members and patients," it said.
South Sudan erupted in violence on December 15 when rebels loyal to ousted Vice President Riek Machar tried to stage a coup.
Since then, militia loyal to the ousted leader have battled government forces. Violence has quickly spread with reports of mass killings emerging nationwide.
The government and rebels signed a cease-fire deal last week calling for an immediate end to all military operations and a freeze of forces wherever they are, but it has not yet brought an end to all fighting.
The parties also agreed not to attack civilians and to refrain from rape, sexual abuse and torture. Supply routes for humanitarian aid are to be opened to reach displaced populations.
U.N. humanitarian chief Valerie Amos, speaking on a visit to South Sudan, said she hoped the cease-fire agreement would help to restore stability.
"I am encouraged by the agreement ... that was signed last week in Addis Ababa, Ethiopia. I hope [it] will lead to an environment where people will feel able to return to their homes and rebuild their lives," Amos said Wednesday.
South Sudan seceded from Sudan in 2011 after decades of war, making it the world's youngest nation.