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 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.

There are fears that the fighting could re-ignite a full-blown civil war in the world's youngest nation.

Jonglei, one of the most food-insecure parts of the country with severe health needs, has seen an estimated 280,000 people displaced by fighting and aerial bombardments since December, the UN said.

MSF stated that prior to the airstrike, they had received information about a possible attack, allowing them to evacuate the hospital and discharge patients hours before the event. However, the damage included the destruction of the hospital’s main warehouse and loss of critical medical supplies.

MSF highlighted that it was the only health provider serving around 250,000 people in the area, warning that such attacks mean local communities will be left without healthcare.

Gul Badshah, MSF's operations manager, remarked that it is unacceptable for humanitarian organizations to be targeted amidst growing needs in the country. In recent months, MSF has faced multiple targeted attacks, forcing the shutdown of facilities and limiting necessary healthcare access.

The ongoing violence is a continuation of the turmoil that began in 2013, marked by ethnic tensions and a lack of implementation of past peace deals, leading to a humanitarian crisis that continues to worsen in South Sudan.