At least 10 soldiers were killed and another 50 were reported missing after friendly fire caused a South Sudanese military boat to sink on the Nile river, the army said Saturday.

"It was an accident. The boat was travelling at night and passed before a (control) post at Lul, which tried to stop the boat. When it did not stop they fired at the boat and it sank," army spokesman Philip Aguer told AFP, adding that there were about 170 soldiers on board.