An Iranian passenger jet has crashed, killing all 168 people on board.The Russian-built Tupolev plane, operated by Iran’s Caspian Airlines, is reported to have caught fire after suffering technical problems. The plane was travelling from Tehran to the Armenian capital. It crashed into farmland near the northwestern city of Qazvin, about 15 minutes after take-off. This is the worst air crash in Iran for six years. Air safety experts say Iran has a poor record, with a string of crashes in the past few decades, many involving Russian-made aircraft. Observers say US sanctions against Iran have prevented it from buying new aircraft or spares from the West. It has been forced to supplement its ageing fleet with aircraft from the former Soviet Union. The passenger list included 151 adults and two children and 15 crew. A former member of parliament is said to have been on board, along with the wife of the head of Georgia’s diplomatic mission in Iran.