News that the US central bank would keep borrowing costs at zero was broadly welcomed across Asia, with most stock markets up, as it eased concerns about a feared flight of capital from the region's struggling economies.
It also weakened the greenback, making dollar-priced oil less expensive for traders with weaker currencies.
However, Fed chief Janet Yellen said in a news conference that bank policymakers cited the ongoing crisis in China and recent turmoil on world markets as playing a role in the decision.
It said the Fed policymakers "would like to see the extent to which these developments have impacted the US economy given the strong financial interconnectedness".
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On oil markets US benchmark West Texas Intermediate for October delivery fell 13 cents to USD 46.77 today and Brent crude for November rose six cents to USD 49.14.
"The impact of the... Decision is somewhat mixed," said Bernard Aw, market strategist at IG Markets in Singapore.
Oil prices had surged on Wednesday after the US Department of Energy revealed a 2.1 million barrel drop in inventories, fuelling hopes of a pick-up in demand in the world's biggest economy.