Russia has called on South Sudan to punish those responsible for shooting down a United Nations helicopter, killing all four Russian crew members.

In a Foreign Ministry statement Saturday, Moscow urged South Sudanese officials to take steps to make sure such incidents do not happen again.

The statement said the “tragic occurrence” underscored the need to provide security for U.N. peacekeeping missions.

South Sudan's army shot down the U.N. helicopter Friday. A South Sudan military spokesman said troops mistook the helicopter for an aircraft supplying weapons to rebels.

U.N. Secretary General Ban Ki-moon strongly condemned the attack, saying the U.N. helicopter was clearly marked. He called on the government to immediately carry out an investigation.

The United Nations says the flight was on a reconnaissance mission when it went down Friday in the eastern state of Jonglei. An initial U.N. report said the helicopter had simply crashed.

The president of the U.N. Security Council, Moroccan Ambassador Mohammed Loulichki, says the shooting is a grave violation of the U.N.'s mandate in South Sudan and jeopardizes the U.N. operation there, known as UNMISS.

“The members of the Security Council strongly deplore the shooting down in Jonglei state South Sudan on December 21, 2012, by the Sudan People's Liberation Army on UNMISS helicopter performing a reconnaissance flight to the area with four Russian crew members all of whom were confirmed dead.”