Investing.com - West Texas Intermediate oil futures fell below the $48-level on Monday, as ongoing worries over high domestic U.S. oil production weighed.
On the New York Mercantile Exchange, crude oil for September delivery hit a session low of $47.77 a barrel before trading at $47.96 during European morning hours, down 18 cents, or 0.38%.
On Friday, Nymex oil futures hit $47.72, a level not seen since April 1, before ending at $48.14, down 31 cents, or 0.64%.
New York-traded oil futures tumbled $2.97, or 5.99%, last week, the sixth consecutive weekly loss, as worries over high domestic U.S. oil production weighed.
According to industry research group Baker Hughes (NYSE:BHI), the number of rigs drilling for oil in the U.S. increased by 21 last week to 659, the most since May.
Elsewhere, on the ICE Futures Exchange in London, Brent oil for September delivery inched down 12 cents, or 0.23%, to trade at $54.49 a barrel. Prices slumped to $54.30 on Friday, the weakest level since April 2.
London-traded Brent futures lost $2.50, or 4.34%, last week, the fourth straight weekly decline, amid concerns a resumption of Iranian oil exports will add to a global glut.
Iran and six world powers reached a long-awaited nuclear deal earlier in the month that would end sanctions on Tehran in exchange for curbs on the country's disputed nuclear program. Iran reportedly hoards 30 million barrels of oil in its reserves ready for export.
Global oil production is outpacing demand following a boom in U.S. shale oil production and after a decision by the Organization of Petroleum Exporting Countries last year not to cut production.
Meanwhile, the spread between the Brent and the WTI crude contracts stood at $6.53 a barrel, compared to $6.48 by close of trade on Friday.