May 22 (Reuters) - The Russian rouble firmed marginally on Monday, overcoming lower oil prices to move back past the 80 mark against the dollar on the promise of increased supply of foreign currency as exporters prepare for tax payments.
At 0705 GMT, the rouble was 0.1% stronger against the dollar at 79.90 and was unchanged versus the euro at 86.49. It had firmed 0.2% against the yuan to 11.35.
Month-end tax payments that usually lead exporters to convert foreign currency revenue to meet local liabilities should provide the rouble with some support. Those taxes are due on May 29.
Brent crude oil, a global benchmark for Russia's main export, was down 1% at $74.82 a barrel.
Russian stock indexes were higher.
The dollar-denominated RTS index was up 0.7% to 1,043.8 points. The rouble-based MOEX Russian index was 0.8% higher at 2,647.8 points.
Russian indexes eased on Friday as the West imposed new sanctions on some metals companies, but dividend announcements by "heavyweights" like Rosneft and Gazprom this week could propel the market to new highs, said Sinara Investment Bank.
Shares in Nasdaq-listed tech giant Yandex hit a more than one-year high in early trade on Monday, extending gains from the previous session, and up around 4% on the day.
Yandex, often dubbed "Russia's Google", has received bids from Russian billionaires for assets it is seeking to divest within the country that value them at some $14 billion, three people familiar with the matter told Reuters on Friday.
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(Reporting by Alexander Marrow; Editing by Hugh Lawson)
