[NEW YORK] Brent futures fell and US crude turned lower on Friday as both contracts headed for their fourth straight weekly declines as weak economic data from China added pressure on oil prices.
US crude losses follow Thursday's fall into bear market territory, with it US$48.45 a barrel settlement off 21 per cent from the June 10 close at US$61.43. A 20 per cent downturn is considered by many traders to constitute a bear market.
China's factory sector contracted by the most in 15 months in July, a preliminary private survey showed on Friday, a worse-than-expected result that follows a stock market slide that began in June.
Eurozone business activity also started the second half on a less secure footing than expected, with Markit's flash PMI falling to 53.7 this month from June's four-year high of 54.2.
Brent September crude was down 85 cents at US$54.42 a barrel at 11 am EDT (1500 GMT), near its US$54.40 intraday low, the lowest front-month price since early April.
US September crude was down 45 cents at US$48, with the US$47.96 session low also the lowest price since April 1.
Oil traders awaited fresh oil rig data from Baker Hughes Inc around 1700 GMT on Friday, to see if the price declines continue to curb drilling activity.
"We feel that US production could begin to show significant slippage while oil rig counts post new lows," Jim Ritterbusch, president at Ritterbusch & Associates, said in a note on Friday.
The dollar's strength also applied pressure, as a stronger US dollar makes greenback-denominated oil more expensive for consumers using other currencies.