Oil fell towards $96 a barrel on Wednesday as rising supply from Africa and Iraq offset mounting tensions in the Middle East and better-than-expected data in China.
Weak European economic data and a rise in oil exports from Iraq, Libya and Nigeria have weakened the oil price, which is down around 14 percent this quarter, the biggest quarterly drop since the second quarter of 2012.
Brent for November delivery fell 55 cents to $96.30 a barrel by 1258 GMT. It was down more than 6 percent for the month so far, the biggest monthly drop since April 2013.
U.S. crude fell 17 cents to $91.39 a barrel.
"We have restocking (because of increased exports) from Libya, and crude oil is also weak because of refinery maintenance," said Olivier Jakob of consultancy Petromatrix in Zug, Switzerland.
Libya's national oil production is currently at 900,000 barrels per day (bpd) with the major El Sharara oilfield at 200,000 bpd, an official with the National Oil Corporation said on Wednesday.
Exports from Iraq's southern terminals have averaged 2.58 million bpd, according to shipping data for the first 23 days of September tracked by Reuters, up from the August average of 2.38 million.
Nigeria's oil exports are expected to hit a 14-month high in November, adding more light, sweet crude oil to an already well supplied market.
The European Central Bank faces an uphill task to spur growth as euro zone business activity expanded at a slightly weaker pace than expected in September as firms cut prices for the 30th month in a row, a survey showed on Tuesday.
Manufacturing and services output in the bloc's top two economies, Germany and France, has also slowed.
In China, August crude inventories, excluding strategic reserves, were higher than the previous month.
China's 2015 economic growth, however, is expected to be "well above" 7 percent, according to the International Monetary Fund on Wednesday.
Technical analysts said that there is little to stop oil slipping towards $90 per barrel.
"There's not a lot to stop the trend breaking down further," said Lynnden Branigan, a technical analyst at Barclays Capital.
"There's extreme selling pressure, and after the July 2012 low of $95.30, the next support is at $91.85."
U.S. investors were waiting for weekly oil inventory data from the Energy Information Administration later on Wednesday for indications about demand in the world's largest oil consumer.
Crude inventories fell by 6.5 million barrels in the week to Sept. 19, data from industry group the American Petroleum Institute showed on Tuesday. Analysts in a Reuters poll were expecting inventories to have risen by 400,000 barrels.
(By Simon Falush; Additional reporting by Seng Li Peng in Singapore; editing by Jane Baird and William Hardy)