Russian diamond miner Alrosa has said it plans to invest $2.8bn in three mines by 2014 with an overall capacity of nearly six million metric tonnes of diamond ore each year.

The company plans to establish the underground mines to maintain the miner’s mineral base and sustain its standing in the international market, reports.

Alrosa accounts for nearly a quarter of international diamond output, the news service said.

Throughout September Alrosa will restart all mining and processing operations that it had previously shut down because of a drop in demand.