June 16 (Reuters) - Russian retailer Magnit on Friday said it was offering to buy back blocked shares at a 50% discount from foreign shareholders no longer able to trade its Moscow-listed securities.

It is the first proposal of its kind by a Russian company since sweeping Western sanctions over Moscow's invasion of Ukraine and subsequent Russian countermeasures deprived many foreign investors of the ability to trade in Russian securities.

The tender offer is voluntary, Magnit said, and concerned a total of 10,191,135 shares, or around 10% of Magnit's outstanding shares. The tender price was 2,215 roubles per share.

"That is, it takes into account a 50% discount from the weghted average price of Magnit shares for the last half a year," Magnit said, meaning a total of 22.57 billion roubles could be spent on the buyback.

A Russian government commission has determined that foreign companies selling assets in Russia must do so at a 50% discount. Magnit said it had sought approvals from the government.

(Reporting by Alexander Marrow, Editing by Louise Heavens)