A powerful burst of radio waves from space has been observed by Australian and U.S scientists, who say they have never seen anything like it before.

They say the phenomenon could offer a new way to search for colliding stars or dying black holes.

The scientists thought the extremely brief but strong signal was about 3 billion light years away; a light year being about 10 trillion kilometres, the distance light travels in a year.

They believe the burst was a catastrophic event from another galaxy and may have been produced by the collision of two neutron stars or the death throes of an evaporating black hole.