Moscow presents the plan as a way for both Russian and foreign investors to free up assets that have been blocked by Western sanctions and Russian counter-measures since the start of the conflict in Ukraine more than two years ago.

The finance ministry has appointed Voronezh-based broker Investitsionnaya Palata (Investment Chamber) to run the scheme. The broker on Monday said it had set starting prices for purchasing foreign securities and said retail investors wishing to take part could submit offers until May 8.

Russian-owned foreign securities will be pooled into lots for which foreign buyers can bid between June 3 and July 5, with payment from special "type-C" accounts in Russia, which are otherwise effectively blocked.

"The offers submitted by Russian private investors will be irrevocable until September 1, 2024," the broker said in a statement. "After submitting their offers, sellers will be temporarily unable to dispose of the foreign securities offered for purchase but will retain ownership."

As a result of sanctions, more than 3.5 million Russians have frozen assets abroad worth around 1.5 trillion roubles ($16.2 billion). They can apply to sell up to 100,000 roubles worth of foreign securities under the scheme. According to the central bank, 80% of affected Russian investors have frozen foreign assets below that threshold.

Some Russian investors have expressed concern that sanctions on Russia's National Settlement Depository (NSD) may dissuade foreign investors from taking part.

Britain's Foreign, Commonwealth & Development Office this month said Russia's appointment of a broker to manage the scheme had no relevance or impact on sanctions.

A spokesperson said it highlighted "increasingly desperate attempts" by President Vladimir Putin to mitigate the effect of sanctions.

($1 = 92.7900 roubles)