The Malaysian passenger jet that crashed near the Ukraine-Russia border was shot down by missile, US media reported on Thursday.

A radar system saw a surface-to-air missile system turn on and track an aircraft right before Malaysian airliner MH17 was shot down, a senior US official told CNN.

A second system saw a heat signature at the time the airliner was hit, the official added.

The US is analyzing the trajectory of the missile to try to learn where the attack came from and has not determined who was responsible, CNN reported.

The Washington Post quoted a US official as saying that American intelligence agencies had confirmed that the plane was shot down by a surface-to-air missile.

The official, who was not authorized to speak on the record about an early intelligence assessment, told the newspaper that government analysts were scrambling to determine who fired the missile.