MOSCOW, March 25 (Reuters) - The Russian rouble firmed slightly at market opening on Monday, supported by increased demand amid month-end tax payments, while stocks headed lower as the market digested a much-anticipated U.S. report on Russian interference in the 2016 U.S. election.

A 22-month long investigation led by Special Counsel Robert Mueller ended with a finding that no one in President Donald Trump’s campaign “conspired or coordinated with the Russian government” in the 2016 election, a report showed on Sunday.

The news dominated Russian media on Monday, raising hopes that Washington could refrain from slapping more sanctions against Moscow, something that proved to be harmful to Russian markets in the past few years.

“The probability of harsh sanctions against Russia declines,” said Alexei Antonov, an analyst at Alor Brokerage.

Russian officials welcomed the Mueller’s report, with a senior lawmaker proposing a “reset” in ties with Washington.

The rouble gained 0.2 percent to 64.52 at 0727 GMT , heading towards its strongest level since August 2018 of 63.63 it hit last week.

Versus the euro, the rouble was 0.2 percent stronger at 72.94.

The rouble retains support from month-end tax payments that usually prompt export-focused companies to convert their dollar revenues to meet local liabilities. This month, tax payments are higher than usual.

The Russian bond market showed a muted reaction to the U.S. report.

Yields of 10-year benchmark OFZ treasury bonds, which move inversely with their prices, declined to 8.28 percent from 8.31 percent seen late on Friday, the day when they moved higher following the central bank’s decision to hold rates.

Brent crude oil, a global benchmark for Russia’s main export, shed 0.5 percent to $66.70 a barrel but remained supportive for Russian assets as it hovered near 2019 highs.

Still, Russian stock indexes inched lower. The dollar-denominated RTS index was down 0.2 percent to 1,210.9 points, while the rouble-based MOEX Russian index dropped 0.5 percent to 2,479.7 points.

For Russian equities guide see

For Russian treasury bonds see (Reporting by Andrey Ostroukh Additional reporting by Gabrielle Tétrault-Farber and Polina Nikolskaya; Editing by Toby Chopra)