MOSCOW, Nov 28 (Reuters) - Russia's SPB Exchange, which specialises in trading foreign shares, said on Tuesday it would transfer almost a third of clients' funds held in foreign currency to them in roubles, with U.S. sanctions blocking access to the rest of the funds for now.

The U.S. Treasury in early November targeted SPB as part of sweeping new measures that also aim to curb Russia's future energy capabilities and sanctions evasion. This forced SPB to halt trading of shares on the exchange and to tweak its strategy to focus on settlements in roubles.

SPB said it had agreed with brokers on a mechanism to distribute a portion of funds now trapped, referring to funds, denominated in U.S. dollars, Hong Kong dollars, China's yuan and the Kazakh tenge, amounting to the equivalent of 5.9 billion roubles ($66.44 million) and representing 31.05% of clients' total FX funds.

SPB has distributed the funds to brokers who will independently determine how to pass them on to clients, SPB said.

"(Brokers') clients will be able to withdraw these funds only in roubles, as settlements in foreign currencies are currently inaccessible to SPB Exchange," SPB said.

From Tuesday, the remaining funds in foreign currencies and securities that the exchange is currently unable to clear or settle would be transferred temporarily to non-trading entities, SPB said.

The exchange said its international legal advisors would deliver their opinion by Dec. 4, at which time more information would be provided. Trading of foreign securities on the exchange remains suspended.

SPB has endured a turbulent month. Following sanctions and the trading suspension, SPB was forced on Monday to deny that it had filed for bankruptcy, blaming fraudsters for filings with a Russian court and promising that it would push for a criminal investigation.

"What we saw yesterday ... is not an abuse of rights, it is almost a crime," Mikhail Mamuta, head of consumer protection at the central bank, said on Tuesday. "I think law enforcement should sort out what happened."

SPB's Moscow-listed shares, which recovered after slumping over 30% to a record low at one point on Monday, were flat on Tuesday. ($1 = 88.8000 roubles) (Reporting by Alexander Marrow and Elena Fabrichnaya; Editing by Susan Fenton)