Brent crude slipped further below $107 a barrel on Friday on concern about higher supply and faltering demand, despite signs of faster economic growth in the world's second-largest consumer China.
Worries that the escalating war in Syria could disrupt Middle East oil supplies pushed Brent to a six-month high above $117 in August. But prices have dropped more than $10 a barrel since then and some analysts see further falls ahead.
U.S. crude oil has been depressed by a seasonal dip in demand and increasing domestic oil production that has boosted stockpiles, particularly on the U.S. Gulf coast.
Brent crude for December was down 30 cents a barrel to $106.69 by 1255 GMT, or nearly 3 percent lower on the week, falling for a third day.
U.S. crude oil was up 42 cents at $97.53, although still down around 3.5 percent on the week, its biggest weekly loss since June.
"But the fact that prices have not bounced back is quite bearish. The risks are still to the downside."
"Balances are not as tight as we, or the market, had expected," said Virendra Chauhan, oil analyst at London-based consultancy Energy Aspects.
"The worst of this year's supply shortfalls is now behind us, with maintenance at non-OPEC fields largely complete and some of the lost OPEC production also coming back in Libya, Nigeria and Iraq," Chauhan added.
Oil markets found some support from Chinese data on Thursday pointing to faster economic growth in the world's second-biggest oil user.
China's factory output expanded at its fastest pace in seven months in October as policymakers sought to ensure a steady, broad-based recovery.
In the United States, while overall manufacturing fell last month, Friday's durable goods report showed new orders outside of transportation equipment fell in September in a possible sign companies were holding back on investments due to uncertainty over government spending.
But fading geopolitical risk is curbing speculative interest in oil with signs of a possible rapprochement between Iran and the West raising expectations of some easing of sanctions and, possibly, more Iranian oil exports.
"The prospect for 2014 is already of a big surplus, and, on top of that, there is the chance of a return to the market of more Iranian oil - barrels no one needs," Commerzbank's Fritsch said.