South Sudan's army shot down a United Nations peacekeeping helicopter on Friday. All four of the Russian crew members who were on board were killed, Reuters reported.
According to the UN, cited by Reuters, the helicopter was on a reconnaissance mission in an area where South Sudan's Army has been fighting rebel militias. The BBC reported that the helicopter was clearly marked.
UN Chief Ban Ki-Moon has strongly condemned the attack.
The Agence France Presse reported that the helicopter was hit while flying over Jonglei state in eastern South Sudan. A UN official explained that because it's currently the wet season in South Sudan, the helicopter was looking for dry spaces to land peacekeepers if that became necessary.
Jonglei has been stricken by ethnic strife and rebellion since South Sudan's independence in July of last year. The state was in the front lines in nearly four decades of civil war between the Khartoum government and South Sudan that left 200 million dead.