Russia 's foreign minister calls on South Sudan to punish those responsible . Four Russians died when South Sudanese forces shot down a U.N. helicopter . South Sudan 's armed forces say the incident was an accident . Comment:
Russia 's foreign minister calls on South Sudan to punish those responsible . Four Russians died when South Sudanese forces shot down a U.N. helicopter . South Sudan 's armed forces say the incident was an accident . U.N. chief Ban Ki-Moon has condemned the shooting down of the aircraft .