A mighty blast of radiation from an exploding star may have wiped out a significant proportion of sea life around 450 million years ago, scientists claim.

New research points to a phenomenon called a 'gamma ray burst', which could have been responsible for the so-called Ordovican mass extinction in which 50-60% of all marine invertebrates disappeared.

Gamma ray bursts are hugely powerful surges of radiation.

They are thought to caused when a star explodes, and their force is more than 15 times stronger than the energy emitted from the sun itself.

Scientists from the US space agency Nasa and the University of Kansas say the mass eradication of many near-the-surface fish and mammals can be explained by a gamma ray burst.

Marine life which lived at deeper levels would probably have survived the gamma blast, say the scientists.

This wasn't exactly a case of a 'near neighbour' exploding, either - the experts say the blast could have occurred as many as 6,000 light years away from planet Earth, and still caused so much havoc with the ozone layer and at ground level.

This new theory replaces the notion that a severe ice age was responsible for the loss of so much animal and marine life at that stage of earth's development.

The research was printed in the latest issue of Astrophysical Journal Letters.