China said on Monday it was "deeply concerned" after Iranian President Ebrahim Raisi's helicopter went missing in what Tehran's state media described as an accident, and pledged to help the rescue operation

President Raisi, the foreign minister and all the passengers in the helicopter were killed in the crash, senior Iranian official told Reuters

Rescuers in Iran were racing on Sunday to find the crash site of a helicopter that was carrying President Ebrahim Raisi to find out the fate of all those on board. Below is brief outline of what Iran's constitution says happens if a president is incapacitated or dies in office