UPDATE 1-Russian search engine Yandex ups 2018 revenue forecast

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MOSCOW, Oct 29 (Reuters) - Russia's biggest internet search engine Yandex raised its 2018 revenue forecast on Monday and said it gained market share in the third quarter year-on-year, boosting its shares.

The company, which competes with the likes of and Mail.Ru, said it now expected revenue to grow 35-38 percent in rouble terms, up from 25-30 percent previously.

The new forecast excludes Yandex.Market, a joint venture with Russia's largest lender Sberbank set up in April and tipped as a local version of U.S. online retail giant Amazon .

Yandex's share of Russia's search market, including mobile, averaged 55.9 percent in the third quarter, up from 54.9 percent in the same quarter last year, though down from 56.2 percent in the second quarter, according to Yandex.Radar

Revenue excluding Yandex.Market rose 44 percent year-on-year to 32.6 billion roubles ($497 million), while adjusted net income excluding Yandex.Market leapt 167 percent to 6 billion roubles.

Following the results, Yandex's Moscow-listed shares extended gains and were up 8.7 percent at 1049 GMT, outperforming a 1.1 percent rise in the benchmark MOEX Index . The company's U.S.-listed shares were up 6 percent in a premarket trade.

($1 = 65.6075 roubles) (Reporting by Anastasia Teterevleva; Writing by Polina Devitt; Editing by Andrey Ostroukh and Mark Potter)