Crude oil prices extended its losses on Friday to post their biggest weekly fall in eight months amid intensifying concerns over supply glut.

Brent crude, the global benchmark for oil, fell 1% to $43.61 a barrel, reaching the lowest levels not seen in more than six years.

Overall, oil prices have fallen 8% this week, witnessing the largest weekly losses since March this year. In seven out of the past eight sessions, oil prices had been on a decline.

The official data released in the US on Thursday showed oil inventories in the country rose to their highest level since April, accelerating the slide in oil prices.

Further, oil prices came under pressure after a report from oil consultancy firm Baker Hughes showed an increase in oil rig count in the US for the first time in the past 11 months. The weekly rig count went up by two to 574 against 1,578 in the same period last year.

The decline in oil prices this week is also due to reduced demand in China and a strengthening US dollar.

"Driving the move lower is evidence of a general economic slowdown outside the US, combined with supply gluts in many different commodities," The Wall Street Journal quoted Bill O'Neill, a broker with Logic Advisors, as saying.

The International Energy Agency (IEA) estimated the global oil demand to slow to 1.2 million barrels a day in 2016, after touching a five-year high of 1.8 million barrels a day this year.

"Everybody right now is hearing, 'Too much oil in the world', " said Michael Hiley, an energy trader at brokerage LPS Partners Inc. "When you do have something from IEA that points out how much is there, it's sort of a wake-up call."

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