LONDON (AFP) - Oil prices plunged Monday to seven-month lows near 91 dollars on prospects of weaker energy demand amid a worsening global financial crisis after Lehman Brothers' bankruptcy, analysts said. Brent North Sea crude for October delivery tumbled 4.84 dollars to 92.74 dollars after earlier hitting 91.17 dollars a barrel " the lowest level since February. New York's main contract, light sweet crude for October, lost 4.24 dollars to 96.94 dollars. Prices fell "as wider financial woes raised further concerns of slowing demand for oil," Barclays Capital analysts said. Financial markets were rocked as US banking giant Lehman Brothers filed for bankruptcy after failing to find a buyer, having been crippled by the US subprime home loan crisis and related credit crunch. "Turmoil in the financial markets hurt sentiment and reinforced concerns about weaker oil demand growth," said Sucden analyst Michael Davies. Oil prices were also weighed down by news that damage to US oil platforms caused by Hurricane Ike had not been as bad as feared. US officials said that Ike, which slammed into the US Gulf Coast on Saturday, had damaged about 10 oil platforms in the Gulf of Mexico where major energy installations are located. "The initial perception is that there hasn't been much structural damage to oil and refinery infrastructure," said David Moore, a Sydney-based commodity strategist with the Commonwealth Bank of Australia. Oil prices are down by more than a third in value from record levels of above 147 dollars reached in July, as investors grow increasingly pessimistic about weakening energy demand amid signs the global economy is slowing down. Fuelling investor concerns was the announcement Monday that Lehman Brothers would file for bankruptcy after the investment bank, in desperate need of a capital injection, had failed to find a buyer. Global stock markets were badly hit as a result. The US Federal Reserve, the European Central Bank and Bank of England responded to the latest gloom by pumping billions of dollars into financial markets in an effort to ensure adequate liquidity. A series of reports highlighting a fall in demand were published last week. The US Department of Energy lowered its forecasts for 2009 global crude oil demand and the International Energy Agency cut its estimate for demand growth this year by 100,000 barrels per day and for 2009, by 140,000 bpd. News that militants had attacked a Shell facility in Nigeria's restive southern Delta region, a day after an armed group declared an "oil war," had little immediate impact given the backdrop of bad news from other quarters, traders said.