The Russian Direct Investment Fund (RDIF) and its co-investors, including sovereign funds in the Middle East and Asia, have bought about half of the shares in state-controlled diamond miner Alrosa offered in a placing, a source familiar with the process said.

However, the stake bought by the state-backed RDIF is significantly smaller than those taken by the international funds, the source said, adding that there were Western investors among them.

The sale of the 10.9 percent stake in Alrosa, the world's largest producer of rough diamonds in carat terms, ranked as Russia's largest privatisation in recent years as the country seeks ways to bolster finances which have been hit by weak oil prices.

The Russian government priced the shares at 65 roubles ($1.02) per share, raising almost $820 million, a source close to the placing said on Saturday.

RDIF said that it took part in the sale but declined to comment on the details.

An official announcement on the outcome of the offer is expected on Monday.