Oil prices fell below $50 on Friday and were poised for their biggest weekly loss in six weeks on doubts over OPEC's planned output cut, even as data showed US oil drillers cut rigs for the first time since June, Reuters reported.
Data by oil services company Baker Hughes Inc (BHI.N) showed US oil drillers cut two rigs this week, ending a 17-week recovery in the rig count.
But the market's attention remained on disagreements at a meeting in Vienna of the Organization of the Petroleum Exporting Countries (OPEC), said James L. Williams, energy economist at WTRG Economics in London, Arkansas.
"A two-rig count is not significant one way or another. That could just be somebody moving rigs," he said. "All of the focus prices-wise is on the OPEC meeting right now ... I don't think we're going to get any positive news just yet."
Oil prices also slumped on news that the FBI had found additional emails relating to Democratic presidential nominee Hillary Clinton's past use of a personal email server for her work as US secretary of state. The US stock market dropped sharply, while the dollar rallied.
Brent crude futures LCOc1 were down more than 2 percent at $49.42 a barrel.
US West Texas Intermediate CLc1 crude fell 2.4 percent to $48.53 a barrel.
The benchmarks are set to show at least a 3 percent drop for the week, the biggest loss since mid-September.