South Sudan should punish those responsible for shooting down a UN helicopter in which four Russian crew members were killed, Russia's foreign ministry has said.
In a statement released on Friday, the ministry also urged South Sudan to take steps to ensure such incidents do not happen again.
The statement named the victims and said the "tragic occurrence" in Africa's newest nation on Friday underscored the need to provide security for UN peacekeeping missions.
"We call on the government of South Sudan to conduct a proper investigation of the incident, to punish those responsible and undertake all measures to guarantee nothing like this happens in the future," it said.
The Mi-8 helicopter owned by Russian air charter company Nizhnevartovskavia was working under a UN contract on a reconnaissance mission in an area where the SPLA, South Sudan's army, has been fighting rebels led by David Yau Yau, according to a UN source.
"They were [crew members] looking for dry landing areas so that we could bring in troops to protect civilians there"
- Kieran Dwyer, UN spokesperson
The SPLA first denied it had shot down the helicopter but later said it had mistaken it for a Sudanese plane supplying rebels, and expressed regret.
The Russian statement said that the downing "raises the issue of the provision of security of UN peacekeeping missions with new acuteness", and that host nations must take the issue extremely seriously.
The helicopter was brought down in South Sudan's Jonglei state and a UN spokesperson said that the South Sudanese army confirmed it had mistakenly fired at the helicopter.
Kieran Dwyer, a spokesperson for the UN department for peace keeping operations, told Al Jazeera on Friday that the crash site had been secured to ensure a thorough investigation.
"They were [crew members] looking for dry landing areas so that we could bring in troops to protect civilians there. We lost contact with that helicopter. We had communications with the national army, the South Sudanese army ... who told us that they had shot at a helicopter in the region," Dwyer said from New York.
"We immediately dispatched a search and rescue operation by air and we found the smoking remains of that helicopter. We've since confirmed that all four crew members on board were killed."
Ban Ki-moon, the UN secretary-general, condemned the shooting down of the "clearly marked" UN helicopter.