OAO Gazprom Neft tumbled the most in seven weeks, leading a slump in U.S.-traded Russian stocks as crude prices extended their decline from this year’s high, prompting investors to withdraw from the world’s largest energy exporter. The oil producer’s American depositary receipts sank 3.8 percent to $11.80 in New York. Trading volume was more than 4 times the daily average of the past three months. It was the worst performance in the Bloomberg Russia-US Equity Index, which slid to a two-week low. Stocks declined as Brent crude, which traders use to price the country’s main export blend, fell 1.6 percent to $56.13, pushing the decline from its May 6 high to 17 percent. Oil, which is selling at about three-fifths its five-year average price, is the country’s biggest export and, along with natural gas, accounts for about half its budget revenue. Lower prices, combined with sanctions linked to the […]