Oil prices edged down amidst strengthening dollar prices and continued oversupply concerns in the crude market.

Brent futures dropped 10 cents compared to Thursday close, trading at $66.60 a barrel, while US crude futures were down 32 cents, trading at $59.56 a barrel, Reuters reported.

"Ample supply in the market weighed down the prices."

Ample supply in the market weighed down the prices, as International Energy Agency says OPEC cartel is producing at least two million barrels of day more oil to meet demand.

Prices were under further pressure as US Energy Information Administration forecast that oil stocks will increase by 1.95 million bpd during the quarter, and remain the same until next year.

The strengthening dollar also added to the pressure, as oil futures priced in dollars made it expensive for buyers in other currencies.

Oil prices got some reprieve from increasing tensions in the Gulf after a Singapore-flagged tanker was fired by Iranian naval vessels.

Oil traders are keenly waiting for the release of oil drilling rig number data in the US later today.