MOSCOW, June 24 (Reuters) - The rouble strengthened on Monday, paring some of the heavy losses sustained at the end of last week, as the impact of U.S. sanctions that led to an exchange trading halt of dollars and euros in Moscow continued to reverberate through Russian markets.

Sanctions on Moscow Exchange and its clearing agent, the National Clearing Centre (NCC), have led to a range of varying prices and spreads as trading shifted to the over-the counter (OTC) market on June 14, obscuring access to reliable pricing for the Russian currency.

On the interbank market, where liquidity can be low as major Russian banks that have been sanctioned cannot participate, the rouble traded 1.3% higher at 87.90 by 0837 GMT against the dollar.

The average dollar-rouble mixed composite rate, calculated by LSEG and based on data from international brokers and counterparties, stood at 88.03, demonstrating the wide spreads - the difference between buying and selling prices - now available.

The central bank's official dollar-rouble rate was set at 87.96 for June 22, calculated on the basis of OTC trading.

The rouble strengthened sharply after the sanctions were imposed amid low liquidity, caused by various technical difficulties to do with interbank limits when closing FX deals on the OTC market and as traders closed foreign currency positions.

Against the yuan, the rouble gained 0.9% to 11.94, according to an analysis of the OTC market.

The yuan had surpassed the dollar to become the most traded currency with the rouble in Moscow before last week's sanctions were imposed. It accounted for a 54% share of the FX market in May.

The rouble has eased from one-year highs reached in mid-June since the government softened capital controls that have been supporting the rouble since October. The volume of foreign currency revenue that exporters must convert into roubles was reduced to 60% from 80%.

Month-end tax payments that usually see exporters convert FX revenues to meet local liabilities also support the rouble.

Brent crude oil, a global benchmark for Russia's main export, was up 0.1% at $85.32 a barrel. (Reporting by Alexander Marrow; Editing by Alexander Smith)