Russia's FSB investigates diamond miner Alrosa in Moscow -source

(Writes through to change the source of information, adds details, context)

By Polina Devitt

MOSCOW, April 6 (Reuters) - Russia's Federal Security Service (FSB) is investigating the Moscow office of Alrosa , the world's biggest diamond miner, in relation to non-core asset sales between 2011 and 2013, a source familiar with the matter told Reuters.

The state-controlled Russian firm, which is the world's largest producer of rough diamonds in carat terms, and the FSB both declined to comment, while the source did not provide any further details.

Together with Anglo American (LSE: AAL.L - news) 's De Beers, Alrosa produces about half the world's rough diamonds.

Alrosa divested several non-core assets between 2011 and 2013, including selling a 51 percent stake in Timir iron ore project to Evraz (LSE: EVR.L - news) , a major Russian steelmaker. It also agreed to sell its gas assets to Russian oil giant Rosneft , but the two sides later failed to agree on the price.

The deals were done under former Alrosa Chief Executive Fyodor Andreev, who held the post between 2009-2014 but died in 2015 after a long-term illness.

Alrosa's shares were down 0.8 percent at 91.4 roubles per share by 1414 GMT compared with a 0.1 percent decline of the broader MICEX index.

Its shares touched 90.5 roubles earlier on Thursday when Interfax news agency cited a source as saying law enforcement officials were removing documents from Alrosa's Moscow office following a request from investigators in Russia's far eastern Yakutia region, where its main production assets are based.

Russia's Investigative Committee and its local office in Yakutia were not available for immediate comment.

The federal government and Yakutia, together with its districts, each hold 33 percent of Alrosa's shares.

The Russian government sold a 10.9 percent stake in Alrosa last year, raising $813 million to plug holes in the budget as part of a privatisation programme.

The state plans to cut its stake in Alrosa further to 25 percent plus one share by 2019, but the finance ministry has said no sale is planned in 2017. (Additional reporting by Svetlana Reiter; Editing by Jack Stubbs and Alexander Smith)