The medical charity, which goes by its French acronym MSF, said the hospital in Jonglei State "was hit in an air strike by the government of South Sudan forces during the night of Tuesday".

The hospital was "evacuated and patients were discharged hours before the attack" after it received information about a possible strike against the city, it said in a statement.

But "one MSF staff member suffered minor injuries", it added.

"The hospital's main warehouse was destroyed during the attack, and we lost most of our critical supplies for providing medical care," said the statement.

In a separate incident, MSF said its health facility in Pieri, also in Jonglei, had been looted on Tuesday by unknown assailants, making it "unusable for the local community".

"Our colleagues from Lankien and Pieri had to flee with the community, and their fate and whereabouts are still unknown, as we are trying to establish communication with them," the organisation said.

Gul Badshah, MSF's operations manager in South Sudan, stressed that the charity had "shared the GPS coordinates of all our facilities with the government and other parties to the conflict before, and we received the confirmation that they are aware of our locations".

"The government of South Sudan armed forces are the only armed party with the capacity to perform aerial attacks in the country," he added.

- 'Unacceptable' -

MSF highlighted that it was the only health provider serving around 250,000 people in Lankien and Pieri, cautioning that attacks on its facilities there "mean that local communities will be left without any healthcare".

Badshah said MSF would "make the necessary decisions to protect the safety of our staff and healthcare facilities" there.

"While we are aware of the enormous needs in the country, we find it unacceptable to be a target for attacks," he said.

MSF has been present in the territory that makes up present-day South Sudan for more than four decades, he noted.

South Sudan is the world's newest sovereign state, which has been beset by civil war, poverty and massive corruption since it was formed in 2011.

MSF said it had experienced eight targeted attacks in South Sudan last year, forcing the closure of two hospitals in Greater Upper Nile and the suspension of general healthcare activities in Jonglei, Upper Nile and Central Equatoria.

The bombing of MSF's hospital this week came after the South Sudanese government in December imposed restrictions on humanitarian access in opposition-held areas of Jonglei, restricting its ability to deliver essential medical assistance there.