(Reuters) – Investors holding depositary receipts in Russia’s sanctioned top banks are facing difficulties in converting them into shares after the European Union targeted Russia’s national clearing house with sanctions, sources and analysts told Reuters.

Russia’s National Settlement Depository (NSD) was sanctioned last Friday, scuppering Moscow’s plan to use it to service the country’s Eurobonds, while the U.S. Treasury on Tuesday has banned U.S. money managers from buying any Russian stocks in secondary markets.

That has complicated already challenging conditions for Russian companies, including dominant lender Sberbank and No. 2 bank VTB, both of which have been disconnected from the SWIFT global payments system over Moscow’s actions in Ukraine and have depositary London-listed receipts.

Depositary receipts are certificates representing shares in a company foreign to where they are traded, which allow investors to trade in overseas stocks.

President Vladimir Putin signed a bill in April requiring Russian companies to delist their depositary receipts to reduce the influence foreign countries could hold over them, except for 15 companies who were granted permission to remain listed abroad.

The London Stock Exchange halted trading in the Russian receipts it lists soon after their prices crashed following the launch of Moscow’s “special military operation” in Ukraine on Feb. 24.

And as sanctions pressure has built, available avenues to convert them into shares have closed, with the restrictions on the NSD the latest thorn in holders’ sides.

“If depository banks consider interaction with the NSD as violating EU sanctions, then converting depositary receipts will be technically impossible for everyone,” VTB’s My Investments broker said last week.

The proportion of receipts is usually around 25% of share capital, said Finam investment consultant Ivan Dubinin, but estimating accurately is difficult at the moment.

Russian banks have been told by Russian authorities to withhold classified data and financial reports.

Dubinin said many foreign investors had exited quickly as Russia began its “special military operation” in Ukraine, but that many still remained, now with no way out.

Non-resident holders have no way to sell their depositary receipts, Dubinin said, while there has been no solution proposed for Russians serviced by foreign brokers.

Sberbank’s programme will close on June 16, with VTB’s following suit on Sept. 1.

A source close to VTB told Reuters the programme would “peter out on its own”.

Sberbank declined to comment on the impact of NSD sanctions, but a Sberbank source told Reuters there was a problem in directly converting receipts stored in European and American clearing houses.

“A large number of orders to convert such receipts are not fulfilled by foreign brokers because they are refusing to conduct transactions with securities of companies on the (United States’) SDN list,” the source said.

(Reporting by Reuters; Editing by Alison Williams)