JUBA - South Sudanese soldiers killed at least 10 troops when they shot and sank one of their own military riverboats in a remote region after mistaking it for an enemy craft, the army said.

The troops opened fire on the boat after ordering it to stop as it passed their position by a river in Upper Nile state midweek, South Sudan's army spokesman (SPLA) Philip Aguer said.

About 50 soldiers are still missing in addition to the 10 killed.

"It was an accident by SPLA soldiers," Aguer said. "They mistook their own boat that was carrying soldiers from Renk to Malakal. It was traveling at night."

The boat sank near the Lul settlement in the west of Upper Nile state, he said.

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