Iran lost a legal fight on Thursday to recover 5,000-year-old treasures it says were looted from one of its most important archaeological sites, known as "The Lost Paradise".

In a ruling that could affect other countries' attempts to secure the return of antiquities, Britain's High Court rejected Iran's claim that it owned the artefacts.

Iran was trying to stop the Barakat Gallery, an antiquities specialist based in London and Beverly Hills, selling vessels made from a grey-green stone called chlorite and decorated with snakes, lions and eagles.

Lawyers acting for Iran said the treasures were among thousands of pieces stolen by looters after floods washed away the topsoil and exposed the ancient city of Jiroft in 2001.

Senior judge Charles Gray said Iran had failed to prove its legal ownership of the jars, cups and other items but gave permission for his ruling to be challenged at the appeal court.

"I have come, with some regret, to the conclusion that Iran has not discharged the burden of establishing its ownership of the antiquities under the laws of Iran," Gray said.

The gallery's London lawyers, Lane & Partners, said the antiquities were mainly bought at auction in Europe and were valued at about 250,000 pounds ($491,000).

They said the court ruling would give countries "pause for thought" before trying to regain artefacts.

"We do understand the Islamic Republic of Iran's desire to preserve (its) rich and diverse heritage," the gallery said in a statement. "However, there must also be protection for those of us who, quite legitimately, are dealing in antiquities.

Iran's lawyers said the ruling was a setback for those trying to stop looters and return antiquities to their countries of origin.

"It will be of great concern to many countries throughout the world as it places their archaeological heritage at further risk," said lawyer Jeremy Scott. "The judgment will have implications for all countries with buried cultural relics, such as Greece, Italy and other Mediterranean states.

"(It) will make it very much easier for British dealers to trade in goods considered looted in their countries of origin."

On Thursday, Greece said it was only a matter of time before Britain was forced to give back the ancient Elgin Marbles, called the Parthenon marbles in Greece.

Prime Minister Costas Karamanlis said the campaign was growing stronger after the U.S. J. Paul Getty Museum returned artefacts to his country.