MOSCOW (Reuters) - A Russian court on Wednesday acquitted the former boss of music download Web site www.allofmp3.com of breaching copyright in a case seen as a key test of Russia's commitment to fighting piracy.

The allofmp3.com Web site angered Western music companies by offering downloads far cheaper than the market price in deals they said breached copyright law.

Denis Kvasov, head of the company which owned the site, was put on trial after entertainment companies EMI Group Plc, NBC Universal and Time Warner Inc. pressed for a prosecution.

"The prosecution did not succeed in presenting persuasive evidence of his involvement in infringing copyright law," said the judge Yekaterina Sharapova.

The site, which has now been closed, was a thorny issue in negotiations between Russia and the United States over Russia's accession to the World Trade Organisation, a key aim of Russian President Vladimir Putin.

Russian marketplaces and underground passes are full of cheap copies of music and film on DVDs and the Russian government has been accused of being too lax on protecting intellectual property rights, a basic principle of WTO membership.

But in July Russia's top negotiator on WTO entry said he thought a deal would be ready by the end of the year.