Oct. 3 (Bloomberg) -- Russia's RTS Index tumbled to its worst week in nine years, forcing the exchange to halt trading, as the biggest slump in commodity prices in a half century sent raw-material producers lower.

OAO GMK Norilsk Nickel, Russia's biggest mining company, had a record loss on the Micex after saying first-half profit sank 33 percent. OAO Gazprom dropped the most since Sept. 16.

The dollar-denominated RTS plunged 7.1 percent to 1,070.98, bringing its weekly drop to 17 percent, the biggest since 1999. Trading was halted three times this week on the RTS exchange, Russia's second-biggest bourse, because of stock declines. The ruble-denominated Micex Index lost 5.3 percent to 924.55 today.

Commodities, as measured by the Reuters/Jefferies CRB Index of 19 raw materials, have tumbled 10 percent this week, the most since at least 1956. Crude oil has fallen 11 percent so far this week on declining U.S. demand and economic growth concerns.

``U.S. consumers are using about a million barrels less of oil a day than they were 18 months ago, and the U.S. financial sector is also bringing money back home, taking a lot of cash out of emerging markets and commodities,'' said Chris Weafer, chief strategist at UralSib Financial Corp. in Moscow.

Norilsk Nickel plunged 18 percent to 2,757.57 rubles, its biggest decline since listing on the Micex last year. The world's largest producer of refined nickel said first-half profit fell to $2.7 billion from $4 billion a year earlier on lower nickel prices and higher costs.

OAO Uralkali, Russia's second-biggest potash producer, sank 8.2 percent to 117.83 rubles after dropping 11 percent yesterday.

Third-Quarter Decline

The 50-stock RTS sank 47 percent in the third quarter, the second-worst among 88 national benchmarks tracked by Bloomberg. Russia suspended trading for two days and pledged more than $150 billion in emergency funding last month as the seizure in capital markets, falling oil prices and a five-day war with Georgia in August drove away investors. About $58.9 billion has left Russian since Aug. 8, BNP Paribas SA said.

``At least half of the market's fall is attributable to domestic causes,'' Andrei Illarionov, a former Kremlin economic adviser, said in an opinion piece in the Moscow Times today.

Russian stocks today fell along with other emerging markets, and the MSCI Emerging Markets Index was headed for its worst weekly drop since July 2002, when oil declined on a report that Nigeria would pull out of OPEC and boost crude production.

Gazprom, VTB Group

Gazprom, the stock with the biggest weighting in the emerging-markets benchmark, fell 5.1 percent to 180.97 rubles. OAO Rosneft, Russia's biggest oil producer, sank 7 percent to 143.22 rubles, the seventh day of declines.

``Clearly the lower oil prices are exacting downward pressure on markets,'' said Yaroslav Lissovolik, chief economist at Deutsche Bank AG's Moscow office.

VTB Group, Russia's second-biggest bank, fell 5.5 percent to 4.57 kopeks. The bank said its Russia corporate unit lost 9.31 billion rubles ($360 million) in September due to ``negative market dynamics.'' The shares have retreated 66 percent since the bank's initial public offering, the world's biggest last year.

To contact the reporter on this story: William Mauldin in Moscow at wmauldin1@bloomberg.net.

Last Updated: October 3, 2008 11:31 EDT