DOHA - Qatar's central bank sought to reassure foreign investors on Thursday that they could change currencies freely, after equity index compiler MSCI said sanctions against Doha had made it more difficult for investors to obtain riyals.

Saudi Arabia, the United Arab Emirates, Bahrain and Egypt cut diplomatic and transport ties with Qatar in June, prompting many Gulf and other foreign banks to reduce their business with Qatari banks. This has distorted the foreign exchange market, where onshore and offshore rates have diverged.

MSCI said on Wednesday that it might therefore shift to using offshore rates to value Qatar's equities market. Since the riyal offshore often trades several percent weaker against the U.S. dollar than onshore, the shift could lead to changes in the weighting of Qatari stocks in MSCI's emerging market index.

The index compiler will take feedback from the investment community on the proposed shift until Dec. 1, and will announce its final decision by Dec. 5. The prospect of a shift helped to push Qatar's stock market .QSI down 0.7 percent on Thursday.

After the close, the central bank issued a statement saying it was committed to providing all the currency requirements of investors, including local and foreign individuals and institutions, at the official exchange rates.

"There are no restrictions on all banking transactions including transfers," it said, stressing that money transfers could move freely into and out of the country at the official exchange rates.

Commercial bankers say liquidity in the foreign exchange market has suffered partly because the central bank and big state-owned Qatari banks have become reluctant to provide currencies when they believe the supply might be used for speculation against the riyal.

The central bank's statement did not address this issue, but said it was "coordinating regularly with all banks and financial institutions to follow up banking operations and ensure the processing of all procedures and transactions as normal."

The statement added that the central bank had much more than the required foreign reserves to cover all investors' requirements. Official data shows its international reserves and foreign currency liquidity fell to $35.6 billion in September, the lowest since at least 2012, from $39.0 billion in August.

Reserves have been depleted by capital outflows in the months since the sanctions were imposed, but analysts believe Qatar does not risk a crisis because it can replenish the reserves from its sovereign wealth fund, which may have around $200 billion of foreign assets.

(Reporting by Hadeel Al Sayegh; Writing by Andrew Torchia; editing by Mark Heinrich) ((Hadeel.AlSayegh@thomsonreuters.com; +971566883310;))