MOSCOW, August 31 (RIA Novosti) - Alrosa, Russia's largest diamond miner, said on Monday it would invest over $2.8 billion by 2014 in three new mines with total annual capacity of about 6 million metric tons of diamond ore.

Alrosa, which accounts for 97% of Russian and 25% of global diamond output, is carrying out a large-scale program of building underground mines to preserve its mineral base and keep its positions on the global market.

The company, in which the Russian government holds a 50.9% stake, said that from September 1 it would fully restart operations at its mining and ore enriching plants, after a forced suspension due to a slump in demand amid the ongoing economic crisis and planned repairs.

Alrosa Group sold raw diamonds worth $2.18 billion and cut diamonds worth $157.5 million in 2008.