(This content was produced in Russia where the law restricts coverage of Russian military operations in Ukraine)

MOSCOW (Reuters) - The rouble firmed to a near four-week high against the dollar in early trade on Friday, supported by month-end tax payments that boost demand for the Russian currency, while shares in fertiliser producer Phosagro surged after strong results.

At 0704 GMT, the rouble was 0.5% stronger against the dollar at 59.20 after briefly hitting 57.70, a level last seen on July 25.

Against the euro, the rouble gained 0.9% to 59.65.

The rouble is set to see support from month-end taxes that usually prompt export-focused companies to increase conversion of their foreign currency revenues to meet local duties.

Year-to-date, the rouble has become the world's best-performing currency as a result of capital controls that Russia imposed after beginning what it calls a special military operation in Ukraine on Feb. 24.

Rouble volatility has subsided after wild swings that saw it hit a record low of 121.53 to the dollar on the Moscow Exchange in March and then rally to a seven-year peak of 50.01 in June.

On the stock market, the dollar-denominated RTS index slid 0.2% to 1,159.4 points. The rouble-based MOEX Russian index was 0.4% lower at 2,186.7 points.

Shares in Phosagro outperformed the market and climbed 4.4% higher on the day after the company said late on Thursday that its net profit rose by 165% in the first half of 2022 and its board recommended to pay 780 roubles ($13.18) per share in dividends.

($1 = 59.20 roubles)

(Reporting by Andrey Ostroukh; editing by Barbara Lewis)