At least seven people were killed and 20 injured in an attack on a hospital and market in South Sudan on Saturday, a medical charity has said, as worries mount that the country could return to all out civil war.

At least seven people were killed and 20 injured and the last remaining hospital and pharmacy in the country's Fangak county were destroyed in bombings, medical charity Medecins Sans Frontieres said on Saturday.

The attack on Saturday in South Sudan caused significant damage to the hospital's pharmacy, destroying all medical supplies.