FRANKFURT, Dec 19 (Reuters) - Austria's Raiffeisen Bank International, one of the banks in Europe most exposed to Russia, said on Tuesday that it would take a nearly 28% stake in Austrian construction group Strabag as both companies try to limit their ties to Russia.

The bank said it would acquire 28.5 million shares in Strabag through its Russian subsidiary for a cash consideration of 1.510 billion euros ($1.66 billion), an unusual move that would reduce the equity of the Russian subsidiary.

The Strabag stake is being sold by Russia-based Rasperia Trading Limited, a company belonging to the sanctioned Russian businessman Oleg Deripaska. Strabag has also been looking for ways to reduce Deripaska's 27.8% holding.

"With this transaction, RBI further reduces its exposure to Russia," RBI said.

Strabag did not immediately respond to a request for comment outside of business hours.

RBI has been studying a spin-off or sale for its business in the country since Russia's invasion of Ukraine last year but has warned that an exit may take some time and was "highly complex".

The European Central Bank at the same time has been keeping up pressure on banks to loosen ties with Russia.

RBI said it would continue to work on a sale, or a spin-off as a fallback.

Eventually, RBI's Russian subsidiary will eventually transfer the Strabag stake to RBI, which it said it would hold as a long-term investment.

Scores of foreign businesses have quit Russia since its full-scale invasion of Ukraine in February 2022 as Western sanctions made it increasingly difficult to stay, but the Kremlin has also introduced measures to control asset sales.

RBI said the transaction still hinged on its own due diligence for sanctions compliance and other regulatory approvals.

($1 = 0.9112 euros)

(Reporting by Tom Sims; Editing by David Evans and Emelia Sithole-Matarise)