Fighting in a South Sudanese state has forced thousands of people to flee into the bush, including patients and staff at hospital run by an international aid agency.

Medecins Sans Frontiers (MSF) said in a statement on Friday that approaching violence in Unity State meant there were no longer any patients or staff left at Leer Hospital.

A team of 30 local MSF staff members, who were among the 240 that fled, took several dozen of the most severely ill patients from Leer Hospital into the bush, fearing for their safety.

Other patients who were well enough to leave on their own accord also escaped.

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"Despite incredibly challenging circumstances, MSF local staff continued running the hospital in Leer for as long as they could," said Raphael Gorgeu, MSF head of mission.

"However, 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.

"Leer Hospital was the only fully functioning hospital in southern Unity State, and now that it is no longer safe to work in this medical facility, more than 270,000 people have no access to health-care."

Violence has swept through South Sudan since December, with the government trying to stop a rebellion led by the former vice-president, Riek Machar.

'Ethnic cleansing'

As violence rages, Machar is also accusing the government of ethnic cleansing and trying to sabotage peace talks.

In an interview with Reuters, Machar branded President Salva Kiir a discredited leader who had lost the people's trust and should resign.

Thousands have been killed and more than half a million have fled their homes since fighting erupted in the capital Juba in mid-December and spread quickly across the oil-producing nation, often following ethnic lines.

The two sides signed a ceasefire on Jan. 23 in the Ethiopian capital Addis Ababa, but each has accused the other of breaking it.

"Salva Kiir has committed atrocities in Juba, he has engaged in ethnic cleansing and he is still involved in the process," Machar said.

Earlier this week, the country's justice minister had said that Machar and six of his closest allies should face treason charges, accusing him of trying to launch a coup.

"I am not aware of why we should face those charges for an alleged coup that never happened," Machar said. "(It) is another attempt to stop peace talks."

Machar has regularly denied starting the violence or trying to seize power, and has accused the president of taking advantage of an outburst of fighting between rival groups of soldiers to round up political rivals.

The United Nations and rights groups say both warring sides have committed atrocities, in a conflict that has taken the
country to the brink of civil war.