MOSCOW, July 27 (Reuters) - Interpol must explain why it has rejected Moscow's two requests to put British hedge fund head and anti-corruption campaigner William Browder on its search list, the Russian Interior Ministry said on Saturday.

The decision is the latest twist in a long-running battle between the government of Russian President Vladimir Putin and Browder, whose investment company Hermitage Capital was once the largest investor in Russia's equity market.

Russia has sentenced U.S.-born Browder in absentia to nine years in prison for large-scale fraud in a case Interpol described as "predominantly political" when the agency refused Moscow's first request to locate Browder in May.

On Friday, Interpol said it had turned down a second request from Russia to locate and arrest Browder, who lives in Britain and now wages a campaign to expose corruption and rights violations.

Russia's Interior Ministry said it was "perplexed" by the decision and demanded Interpol explain its reasoning without delay.

"The Ministry continues to consider Interpol an organisation that is not guided by political decisions or value judgments," the ministry said in a statement posted on its website.

"Consequently, the Russian Interior Ministry counts on receiving in the near future a comprehensive explanation of the official position of Interpol's General Secretariat...in relation to its refusal to execute the request."

Browder has spearheaded an international campaign to expose corruption and human rights violations in Russia following the death in 2009 of Sergei Magnitsky, a lawyer working for Hermitage and investigating a $230 million tax fraud.

Magnitsky was arrested shortly after alleging that Russian officials were involved in the fraud, and later died in prison while awaiting trial, causing an international uproar.

A Russian court on July 11 found Magnitsky posthumously guilty of tax evasion, triggering harsh criticism from the West, and also sentenced Browder to nine years in prison.

Browder is unlikely to be extradited from Britain, where he lives. But inclusion in Interpol's database would have alerted other member countries to look out for him with a view to arresting him and handing him over. (Reporting by Alessandra Prentice; Editing by Mark Trevelyan)

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