A UN helicopter with Russian crew that was downed in South Sudan last week was probably mistaken for one of the Sudanese aircraft with UN markings that frequently violate South Sudan’s airspace, South Sudan’s ambassador to Moscow said in Friday, December 28, RIA Novosti said.

“Sudanese planes with UN logos have repeatedly been spotted in various regions of South Sudan. This leads to terrible confusion, it might have been the cause of this tragic incident,” Chol Deng Alack said.

The helicopter was shot down last Friday on a reconnaissance flight over the state of Jonglei in eastern South Sudan, the UN said in a statement. All four Russian crew members on board were killed. South Sudan’s army has apologized for the downing, saying soldiers mistook the helicopter for an aircraft carrying arms to rebel forces, army spokesman Philip Aguer said.