Three-month aluminium on the London Metal Exchange fell 1.5 percent to $2,284 a tonne, the lowest level since December 8, on the Federal Reserve's warning of "significant" dangers to the U.S. economy and gloomy data out of China.
The Fed's comment came as it unveiled a $400 billion long-term debt purchase plan. Investors disappointed with the stimulus program sold off commodities, which were also weighed down by a firmer dollar .
China's factory sector contracted for a third consecutive month in September as flagging overseas demand put the brakes on new orders, HSBC's China Flash PMI showed on Thursday.