World oil prices slid on Friday as traders paused for breath at the end of a rollercoaster week, during which sentiment was dictated by concerns over the US election and weak demand, dealers said.
Brent North Sea crude for delivery in December fell 18 cents to $107.07 a barrel in London afternoon trade.
New York's main contract, light sweet crude for December or West Texas Intermediate (WTI), shed 34 cents to $84.75 a barrel.
The market suffered volatile swings this week as dealers reacted to the presidential election in the United States, which is the world's biggest crude consuming nation.
Crude futures had tumbled to three-month low levels on Monday as the market fretted over uncertainty over the crucial race between US President Barack Obama and Republican challenger Mitt Romney.
The market swung higher on Tuesday, soaring by more than $3 in line with Wall Street gains and the weaker dollar, as Americans headed to the polls.
But prices plunged on Wednesday, mirroring global equities, as traders woried about a looming "fiscal cliff" in the United States after Obama's re-election and gloomy EU economic forecasts.
Sentiment was also hammered after the European Union lowered its economic forecasts for the eurozone, to a contraction of 0.4 percent this year and miniscule 0.1 percent growth in 2013.
In addition, the market was dented by profit-taking, the strong dollar and rising US crude inventories data that signalled weak demand in the world's biggest oil consuming nation.
On Thursday, crude futures eked out slender gains amid bargain-hunting after the sharp sell-off.
However, traders continue to worry that US political gridlock will prevent a compromise to avoid the "fiscal cliff" of automatic tax rises and spending cuts at the end of the year, which could potentially tip the US back into recession.
At the same time, traders are also awaiting a once-in-a-decade leadership change in China -- the world's biggest energy consuming nation.
Outgoing President Hu Jintao is due to hand over the reins to Vice President Xi Jinping.
"The US election and its implications with regards to the political leaderships ability to handle the approaching fiscal cliff has of course been the main focus and driver behind the turbulence," said SEB bank analyst Filip Petersson.
"Uncertainty with regards to the Chinese leadership change has also been a factor even though almost no one outside the country really seems to know what to make of it.
"Looking at the Brent prices now, we are about a dollar below where we started the week, and considering the lack of bright spots in the global economy at the moment that is not very surprising," Petersson added.
The Organization of Petroleum Exporting Countries meanwhile held to its forecasts of demand for oil this year and next despite uncertainty about the global economy.
Global demand this year would total 88.80 million barrels per day, slightly less by 0.01 mbd from the estimate in October, the cartel said in its monthly report on Friday. Demand last year amounted to 88.04 mbd.
For next year, OPEC predicted that global demand would stand at 89.57 mbd from 89.60 mbd expected a month ago.