An unknown number of aid workers are missing after air strikes hit a hospital in South Sudan, near the Ethiopian border, a charity group says.

The hospital, run by medical charity Doctors Without Borders (MSF) in Jonglei state, was hit in an air strike by the government of South Sudan forces during the night on Tuesday, MSF said. The South Sudan government is yet to comment.

In a separate attack, MSF said its health facility in Pieri, also in Jonglei state, was on the same day looted by unknown assailants, leaving it unusable for the local community.

Our colleagues had to flee with the community and their fate and whereabouts are still unknown, the medical organisation said.

There has been a resurgence in fighting in Jonglei state recently between government forces and those loyal to First Vice-President Riek Machar, who has been suspended from his post after being accused of plotting to overthrow President Salva Kiir.

Fears are growing that the renewed fighting could spark a full-blown civil war in the world's youngest nation.

Jonglei, one of the most food-insecure areas of the country, has seen an estimated 280,000 people displaced by fighting and aerial bombardments since December, according to the UN.

MSF said it was the only health provider serving around 250,000 people in Lankien and Pieri, warning that attacks on its facilities there mean local communities will be left without any healthcare. While we are aware of the enormous needs in the country, we find it unacceptable to be a target for attacks, said Gul Badshah, MSF's operations manager.

The medical charity said it 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 states.

In December, the South Sudanese government imposed restrictions on humanitarian access in opposition-held areas of Jonglei, limiting MSF's ability to deliver essential medical assistance.

The fighting that erupted in 2013, two years after South Sudan's independence, has resulted in a humanitarian crisis that continues to affect millions. A 2018 peace deal ended the civil war that had killed nearly 400,000 people, but it has not been effectively implemented.

As the international community watches closely, the situation continues to deteriorate, raising concerns for both humanitarian workers and civilians caught in the crossfire.