By Simone Humml and Gretel Johnston

Washington (dpa) - US researchers say they have detected gravitational waves, which physicist Albert Einstein first described 100 years ago as "ripples in the fabric of space-time."

Scientists from Caltech and the Massachusetts Institute of Technology (MIT) made the announcement in Washington and other locations around the world. There were immediate suggestions that the discovery could well win them the Nobel Prize in Physics.

The signal detected with LIGO, an observatory with sites on both sides of the United States, was very clear and there was no room for doubt that it was direct evidence of the waves, said Bruce Allen, who is acting director at Germany's Max Planck Institute for Gravitational Physics.

He said two scientists with his group in the northern German city of Hanover were the first to notice the effect.

The announcement may confirm Albert Einstein's last unproven theory, dating from 1916.

According to Einstein's theory, gravitational waves move at the speed of light in a vacuum and bend space. Each accelerated body, therefore, sends gravitational waves, which increase in strength the greater the mass and the faster it moves.

An earlier news release had said the Laser Interferometer Gravitational-Wave Observatory (LIGO) had been used in the research. It is a system of two identical detectors located in Louisiana and Washington states and was built to detect tiny vibrations from passing gravitational waves.