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

MOSCOW, Aug 19 (Reuters) - The rouble strengthened to a near four-week high against the dollar and euro 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.

By 1520 GMT, the rouble was 0.7% stronger against the dollar at 59.12 after briefly hitting 57.70, a level last seen on July 25.

Against the euro, the rouble gained 1.4% to 59.35 , also reaching a near four-week high of 58.5325 during the session.

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 obligations.

But in the longer run, the rouble could give up some gains due to changes in Russia's foreign trade, analysts say.

"Before the end of the year, we expect the start of gradual rouble weakening in the 65-70 corridor to the dollar or euro, influenced by a likely correction in oil prices, as well as an increase in import volumes - due to seasonal factors and recovery after a dip in spring 2022," said Maxim Petronevich, senior economist at Otkritie Research.

Year-to-date, the rouble has become the world's best-performing currency http://fingfx.thomsonreuters.com/gfx/rngs/GLOBAL-CURRENCIES-PERFORMANCE/0100301V041/index.html 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 rose 0.5% to 1,168.0 points. The rouble-based MOEX Russian index was 0.1% lower at 2,192.2 points.

Shares in Phosagro outperformed the market and hit their highest since March, settling up 2.4% 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 and Alexander Marrow; editing by Barbara Lewis and Gareth Jones)