Oil prices fell Friday after the US Federal Reserve kept its main interest rate on hold and following a volatile week for crude.

US benchmark West Texas Intermediate for delivery in October dropped 45 cents to $46.45 a barrel from Thursday's close.

Brent North Sea crude for delivery in November dipped eight cents to trade at $49.00 a barrel in London midday deals.

The Federal Reserve held its key interest rate locked near zero Thursday, citing worries about how the slowdown in China will hit the US economy.

Fed chief Janet Yellen said in a news conference that central bank policymakers cited the ongoing crisis in commodities-hungry China and recent turmoil on world markets as playing a role in the decision.

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.

"In the case of oil, the expected fall of US output should in theory help to support prices, even if major upward moves seem unlikely for the foreseeable future," said Fawad Razaqzada, analyst at Gain Capital trading group.