The increase has in part been driven by a recent widening between prices for U.S. West Texas Intermediate crude and Brent futures WTCLc1-LCOc1.
The spread between the two benchmark's December contracts, which had narrowed earlier in the day, widened out again, to $5.36 a barrel from $5.31 before the data.
Middle Eastern oil producers are concerned the price rise will only stir USA shale producers into more drilling and push prices lower again.
The big draw in crude oil was only partially offset by an increase of 1.6 million barrels in refined gasoline stocks. Gulf Coast refineries have been using more crude as they resumed operations after weeks of shutdowns following Hurricane Harvey. Both oil contracts have fallen sharply since peaking last week, when Brent hit its highest level since July 2015 of nearly $59.50 and WTI rallied to its best level since mid-April of this year.
Due largely to rising US output, Saxo Bank's Hansen said that "an extension of output curbs beyond March (2018) will be needed to ensure continued support for the oil market".
The vote result could see a hostile response from Iraq's central government, as well as from neighbouring countries such as Iran and Turkey and disrupt the flow of as much as 500,000 barrels a day of Kurdish oil exported through a Turkish port.
Last week, the bullish outlook was supported by reports from OPEC about improving compliance rates-in August-along with Turkey's threat to shut down the 500,000-bpd pipeline carrying Kurdish oil to Ceyhan - a threat that Erdogan has for now chose to not go through with. Barkindo added that compliance levels have sent a clear message to the world that these countries are determined to do what is necessary to bring back sustainable market stability. Also, Russia and OPEC's production cut agreement is set to expire in March 2018.
"We will discuss the state of the market and the current situation regarding monitoring and execution of the crude production deal with our colleagues at the Russian Energy Week", Russia's TASS news agency quoted Novak as saying.
The number of rigs drilling for oil in the USA rose by six in the past week to 750, according to oil-field services company Baker Hughes.