(CNN) -- Russia's Foreign Minister Sergey Lavrov on Saturday called on South Sudan to punish those responsible for shooting down a U.N. helicopter and taking the lives of four Russian crew members.
His words come a day after the South Sudanese armed forces admitted to shooting down the helicopter in eastern South Sudan.
"We call on the government of South Sudan to carry out a full investigation of the incident, punish the guilty and take every measure to guarantee that this will never happen again," Lavrov said, in a statement on his website.
The United Nations Mission in South Sudan said Friday four Russian crew members were killed but that there were no passengers on board the aircraft.
The MI-8 helicopter went down near the settlement of Likuangole, in the state of Jonglei, in the country's east, the U.N. mission said. It is investigating the incident.
The Sudan People's Liberation Army said it was an accident, according to spokesman Philip Aguer.
He said the SPLA had contacted the U.N. mission after seeing the helicopter near an SPLA command post but had been told it had no aircraft in the area.
The troops thought the aircraft looked to be the type that had dropped munitions to militias in the area, Aguer said.
U.N. Secretary-General Ban Ki-Moon condemned the shooting down of the helicopter, saying in a statement that it was clearly marked as being a U.N. aircraft.
Ban extended condolences to the crew members and called on the government of South Sudan to bring whoever is responsible to justice.
CNN's Zarifmo Aslamshoyeva contributed to this report.