A Tupolev passenger aircraft crashed in northwestern Iran today and 168 people on board were killed, Iranian media reported.

The Caspian Airlines aircraft was carrying 153 passengers and 15 crew, Reza Jafarzadeh, a spokesman for Iran's aviation organisation, told state television.

State television showed footage of debris from the plane and some body parts.

"It's been a major disaster with pieces of aircraft spread over an area of 200 square metres," a fire brigade official told Iranian state television.

"There was an explosion which left an indentation 10 metres deep in the ground. There was nothing we could do. We tried to put out the fire as best we could," he said.

Other television pictures showed a large crater gouged into farmland with mangled pieces of metal scattered around. Smoke rose from the site as police and bystanders gathered around.

The plane was travelling from Tehran to Yerevan in Armenia when it came down at 11:33 a.m. (0703 GMT) near the city of Qazvin, the official IRNA news agency said.

The plane crashed 16 minutes after take-off from the capital's Imam Khomeini International airport, it said.

The semi-official Fars News Agency quoted a senior provincial official, Sirous Saberi, as saying the plane had experienced technical problems and had tried to do an emergency landing.

"Unfortunately the plane caught fire in the air and it crashed ... different small parts of this plane can be seen on the ground," he said.

Qazvin police commander Massoud Jafari told IRNA, "Evidence shows that this passenger plane has been completely destroyed."

A fire brigade official, Hossein Behzadpour, said firefighters were trying to extinguish the fire.