April 15 (Reuters) - The Russian rouble firmed past 80 per dollar on Friday and stock indexes inched higher, while shares in gold producer Petropavlovsk underperformed the broader market in Moscow trade and at one point fell more than 20% on the day.

Russian shares in Petropavlovsk, which is also listed in London, extended sharp losses suffered on Thursday after the company said it was considering putting itself up for sale, following sanctions on Russia and the risk of countermeasures.

Petropavlovsk shares were down 14% at 8.74 roubles ($0.11) apiece as of 1500 GMT.

The benchmark rouble-based MOEX Russian index pared earlier losses and rose 0.8% to 2,423.9 points, and the dollar-denominated RTS index gained 1.8% to 958.2 points.

The MOEX index is likely to consolidate within the range of 2,400-2,450 on Friday, Promsvyazbank analysts said, adding that there were no strong factors capable of supporting the Russian market at the moment.

Shares in Russia's largest lenders Sberbank and VTB, both sanctioned by the west, added around 1.5% the day after a central bank official said it was quite possible that the Russian banking sector would lose half of its capital.

The Russian financial sector and economy have taken a hit from unprecedented western sanctions designed to punish Moscow for what it calls "a special military operation" in Ukraine that started on Feb. 24.

Russian authorities pledged to support the stock market with money from the rainy-day National Wealth Fund and have imposed capital controls that helped the rouble to recover from all-time lows hit in March.

The rouble gained 1.5% to 79.71 against the dollar , having pulled back from a record low of 121.52 hit on the Moscow Exchange on March 10.

On electronic trading platform EBS, where the rouble fell as low as 160 to the greenback on March 7, the currency traded at 84 on Friday.

Against the euro, the rouble firmed 2% to 85.26 .

The rouble eased this week after the central bank scrapped a 12% commission for buying foreign currency through brokerages and promised to lift a temporary ban on selling foreign exchange cash to individuals from April 18.

But the rouble retains support from export-focused companies that are still obliged to sell their foreign exchange revenues on the domestic market.

This month, companies in Russia are due to pay a record 3 trillion roubles ($37.6 billion) in taxes, for which some export-focused companies need to sell foreign currency, according to analysts surveyed by Reuters. (Reporting by Reuters; Editing by Edmund Klamann and Hugh Lawson)