Oil prices rose on Friday and posted weekly gains, boosted by heightened geopolitical tensions over Iran and strong gasoline futures, while a stronger dollar and concern about the euro zone debt crisis limited gains.
US gasoline futures posted the strongest percentage gain in the oil complex, more than 2 percent, from news a Northeast US refinery was shutting earlier than planned.
Both Brent and US crude saw choppy and low-volume trading. Oil pared gains as the dollar index recovered from early losses and entered positive territory amid caution about the euro zone.
Both crude contracts were on track to post weekly gains, after two straight weekly declines.
A hardline Iranian cleric warned the United Nations and the European Union against siding with London after students and militia stormed British embassy compounds in Tehran earlier this week.
The EU and the United States tightened their sanctions on Thursday as fears over Tehran's nuclear program intensified, increasing concern over a possible disruption to oil flows from the second-largest OPEC producer.
"The Iranian situation is one of those things that could have a really bullish potential impact," said Tony Machacek, energy broker at Jefferies Bache in London.
ICE Brent January crude rose 95 cents to settle at $109.94 a barrel, reaching $110.41 intraday and stalling ahead of Brent's 100-day moving average of $110.55.
Brent posted a weekly gain of 3.3 percent, best weekly percentage gain since the week to Oct 14.
US January crude rose 76 cents to settle at $100.96 barrel, having swung from $99.76 to $101.56. It posted a 4.3 percent weekly gain, best weekly percentage gain since the week to Nov 11.
Brent crude trading volume was 27 percent below its 30-day average, while US volume was 35 percent under its 30-day average.
US employment growth picked up speed in November and the jobless rate dropped to a 2-1/2-year low of 8.6 percent, bolstering the view that the economy was improving.
US nonfarm payrolls increased 120,000 last month, nearly matching expectations for a gain of 122,000, and the relative strength of the report was bolstered by upward revisions to the employment counts for September and October.
"Oil prices are flagging after the US employment data due to exceedingly high expectations that came rushing into the market after the ADP survey earlier in the week showed a surprisingly strong number," said John Kilduff of hedge fund Again Capital LLC in New York.
"There are some troubling signs of economic slowing in the rest of the world that look to be weighing on prices."
US employers added 206,000 private-sector jobs in November, the ADP National Employment Report released on Wednesday said, well above expectations.
While US economic data has been more supportive to oil this week, reports showing a slowing factory sector in China, much of Asia and the euro zone helped limit oil price gains.
British Prime Minister David Cameron threatened to obstruct a Franco-German drive for swift change to the European Union's treaty, highlighting the difficulty leaders face in trying to save the euro.
France and Germany have tried to form a consensus that euro zone economies need to be bound more closely together, suggesting a change to the EU treaty to give Brussels powers to punish euro states that do not keep their budgets under control.
Sunoco's late-Thursday announcement that it had begun to shut its 178,000 barrels-per-day Marcus Hook, Pennsylvania, refinery, ahead of its original plan for a summer 2012 close, supported oil prices.