A Malaysia Airlines plane with 295 people on board is feared to have crashed in the Ukraine amid claims it was shot down.
TV pictures from the scene showed a pall of smoke billowing into the sky apparently from the stricken aircraft.
The plane is thought to be flight MH17 - a Boeing 777-200 travelling from Amsterdam to Kuala Lumpur.
In a tweet Malaysia Airlines said: "Malaysia Airlines has lost contact of MH17 from Amsterdam. The last known position was over Ukrainian airspace. More details to follow."
Ukraine's Interior Minister was quoted as saying the plane had been shot down.
The jet would have been flying at high altitude on an intercontinental flight that took it over the crisis hit region of Ukraine, where the authorities have accused Russia-backed separatists of previous attacks on aircraft.
Earlier today the Ukrainian authorities said one of their fighter jets was shot down by an air-to-air missile from a Russian plane and Ukrainian troops were fired upon by missiles from a village inside Russia.