Iranian state media say a passenger plane has crashed in northwestern Iran, killing all 168 people on board.
State television said Wednesday the Iranian airliner was heading to the Armenian capital of Yerevan when it went down near the northern Iranian city of Qazvin. The plane crashed 16 minutes after taking off from Tehran's Imam Khomeini International Airport.
Reports quote some witnesses as saying the plane was on fire in mid-air.
State television quotes an unidentified witness as saying the plane suddenly fell from the sky and exploded on impact, causing a huge crater. However, the managing director of Iran's airport authority said there were no indications of problems in conversations between the pilot and ground controllers before the crash.
Video footage showed a field littered with small pieces of smoking wreckage from the Caspian Airlines plane. Investigators are searching for the plane's black box (instrument recording device).
Officials said the aircraft was carrying 153 passengers and 15 crew members.
The passengers included Armenians, Georgians and Iranians. Iran says 10 members of its junior judo squad were among those killed.
Iranian President Mahmoud Ahmadinejad has expressed his condolences to the victims' families. Some of those families have gathered at Yerevan's airport.
The Armenian government says President Serzh Sargsyan is cutting short a working trip to return to Yerevan.
Caspian Airlines is a Russian-Iranian joint venture that was founded in the early 1990s.
Iran has frequent plane crashes, often due to poor maintenance of aging planes.
In the past, Tehran has blamed its plane problems, in part, on U.S. sanctions that it says prevent Iran from getting spare parts. But Caspian airliners are Russian-made planes, so U.S. sanctions would not have the same effect on aircraft maintenance.