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In initial deals, London's benchmark FTSE 100 index climbed 0.14 percent to 6,237.66 points compared with Wednesday's close.
In the eurozone, Frankfurt's DAX 30 won 0.41 percent to 10,269.32 points and the CAC 40 in Paris added 0.31 percent to 4,660.17.
Asian equities also piled on fresh gains Thursday in a global rally as investors keep a nervous eye on the US central bank's monetary policy meeting.
The Fed will later decide whether or not to raise interest rates for the first time since 2006, with a decision scheduled for 1800 GMT.