Crude oil prices fell on 5 November, extending losses into a fifth session, as weak data from top energy consumer China fuelled worries about oil demand against a backdrop of a global supply glut.
Brent crude was trading 1.11% lower to $81.90 at 0755 GMT.
US crude was trading 0.80% lower to $76.57.
Data from China showed that the nation's services sector growth weakened in October as new business cooled. The world's second-largest economy is also suffering dismal factory growth.
Avtar Sandu, senior manager for commodities at Phillip Futures, speaking about the China data, told Reuters: "We had expected this. The market is already soft for Brent and the Chinese data is not going to help although the numbers are not a surprise."
Ric Spooner, chief analyst at CMC Markets in Sydney said: "...I think we are in a situation where the oil price needs to fall to a level where it actually results in supply changes. But what that level is, is what everybody is asking."
Oil prices lost more than 2% overnight after Opec-member Saudi Arabia cut export prices to the US, a move designed to combat the shale boom in the world's leading oil consumer.
A grim outlook for Europe, after the European Commission lowered its forecast for eurozone economic growth over the next few years, also weighed on oil prices.
US crude inventory fell 639,000 barrels to 374.9 million in the week to 31 October, compared with analysts' expectations for an increase of 2.2 million barrels, data from industry group the American Petroleum Institute showed on 4 November.
Prices are down some 30% since June.