A United Nations peacekeeping helicopter was shot down on Friday by South Sudan’s army, killing the four Russian crew members onboard.

A United Nations peacekeeping helicopter was shot down on Friday by South Sudan’s army, killing the four Russian crew members onboard.

A UN source said the helicopter was on a reconnaissance mission in an area where the SPLA, South Sudan's army, has been fighting rebels led by David Yau Yau.

Shortly after the attack, UN Secretary General Ban Ki-moon strongly condemned the attack on the "clearly marked" helicopter and in a statement called "on the government of South Sudan to immediately carry out an investigation and bring to account those responsible for this act."

He demanded measures be put in place to prevent any further incidents in South Sudan, where the U.N. mission known as UNMISS, was created after it seceded from Sudan in July 2011.
South Sudan's army first denied it had shot down the Russian helicopter but later said it had mistaken it for a Sudanese plane supplying Yau Yau rebels in Jonglei.

"We regret the incident," army spokesman Philip Aguer said, adding an artillery unit had spotted a plane landing in an area where Yau Yau forces were operating.

"We saw a white plane landing and asked UNMISS whether they had any flight in the area but they denied it. The army opened fire because it thought it was an enemy plane supplying Yau Yau with weapons." he said. "We later heard UNMISS had a flight there. They should have informed us."