London - European equity markets sank on Friday, with the energy sector reeling as world oil prices plummeted to four-year lows following Opec's decision to hold output.
With US financial markets shut on Thursday for Thanksgiving, traders continued to focus on the outcome of this week's Opec oil cartel meeting.
In midday deals, London's benchmark FTSE 100 index fell 0.63% to 6 681.56 points, the Paris CAC 40 shed 0.48% to 4 361.59 and Frankfurt's DAX 30 lost 0.34% to 9 941.27 points compared with Thursday's close.
The 12-nation Organisation of Petroleum Exporting Countries (Opec) decided on Thursday to maintain its output ceiling at 30 million barrels per day, where it has stood for three years, sending prices plunging in an oversupplied market.
London Brent oil for January delivery sank early on Friday to $71.12 per barrel - hitting the lowest level since July 7, 2010.
US benchmark West Texas Intermediate for January meanwhile had slumped to a four-year trough at $67.75.
"The effects of yesterday's Opec decision to maintain its oil output is still working its way through the markets today," said analyst Alastair McCaig at trading firm IG.
"The template for equity markets today has been clear from the beginning. Oil and energy manufacturers are down, while those companies that are oil consumers are up."
In London, shares in British oil major BP slid 3.39% to 411.75 pence, and rival Royal Dutch Shell saw its 'B' share price drop 3.22% to 2 192.5 pence.
In Paris, French oil and gas giant Total shed 3.57% to €44.24.
Slumping oil prices weigh on the energy sector because they eat into company profits.
At the same time, they also boost airline earnings because they slash the cost of jet fuel or kerosene, which is refined from crude.
Air France-KLM shares in Paris had rallied sharply by more than 6% in early on Friday deals, but fell back into the red on profit-taking.
Nearing midday, Air France-KLM was 3.98% lower at €12.78.
British no-frills airline EasyJet meanwhile saw its shares climb 0.55% to 1 642 pence in London.
ETX Capital analyst Daniel Sugarman noted that "the drop in oil price means cheaper running costs" for airlines.
However, shares in International Airlines Group, parent of British Airways, were 0.11% lower at 457.3 pence.
In foreign exchange trade on Friday, the euro dipped to $1.2454 in late morning London deals. That compared with $1.2467 late in New York on Thursday.
The single currency rose slightly to 79.36 pence from 79.22 pence late on Thursday, while the pound dipped to $1.5691 from $1.5736.
On the London Bullion Market, gold slid to $1 184.50 an ounce, compared with $1 194.75 late on Thursday.