Oil prices fell on Thursday as investors were concerned about output rise from the Organization of the Petroleum Exporting Countries (OPEC).

Tanker-tracking firm Petro-Logistics said earlier this week that OPEC's output was up by 145,000 barrels a day last month.

Major oil producers have agreed to reduce supply by 1.8 million barrels a day through next March in order to ease a global glut that has lingered for about three years.

Analysts said OPEC's rising output offset the rise in U.S. fuel demand. The U.S. Energy Information Administration said Wednesday the gasoline demand stood at a record high of 9.842 million barrels per day last week.

The West Texas Intermediate for September Delivery lost 0.56 dollar to settle at 49.03 dollars a barrel on the New York Mercantile Exchange, while Brent crude for October delivery erased 0.35 dollar to close at 52.01 dollars a barrel on the London ICE Futures Exchange.