MOSCOW, Aug 21 (Reuters) - The Russian rouble weakened

slightly against the dollar and China's yuan on Wednesday in a

thin market.

By 0745 GMT, the rouble was 0.6% weaker at 91.65 to

the dollar, according to LSEG data.

Trading in major currencies shifted to the over-the-counter

(OTC) market, obscuring pricing data, after Western sanctions on

the Moscow Exchange and its clearing agent, the National

Clearing Centre, were introduced on June 12.

One-day rouble-dollar futures, which trade on the Moscow

Exchange and serve as guidance for the OTC market rates, were

down 0.14% at 89.87.

The central bank's official exchange rate, which it

calculates using OTC data, was set at 90.69 to the dollar.

According to an analysis of the OTC market, the rouble

weakened by 0.4% to 12.23 against the Chinese yuan, which has

become the most traded foreign currency in Moscow.

It was down 0.5% at 101.93 against the euro,

according to LSEG data.

Brent crude oil, a global benchmark for Russia's

main export, was down 0.1% at $77.07 a barrel on estimates

showing swelling U.S. crude inventories and expectations that

tensions in the Middle East were easing.