OTTAWA, Jan 8 (Reuters) - The initial assessment of Western intelligence agencies is that a Ukrainian airliner which crashed in Iran on Wednesday was not brought down by a missile, said a Canadian security source.

The source, who declined to be identified, said the agencies believed the Boeing 737 plane had suffered a technical malfunction. The Ukraine International Airline jet crashed shortly after takeoff from Tehran, killing all 176 people on board. (Reporting by David Ljunggren; Editing by Amran Abocar and Chizu Nomiyama)