The European single currency slumped to 99.97 yen in London morning trading -- which was the lowest level since December 2000 and the first time it has breached the key 100-yen barrier since June 2001.
It later recovered to stand at 100.19 yen in afternoon trading, still below 100.61 yen on Thursday in New York.
"Euro/yen is the ultimate risk-off trade at the moment," Forex.com research director Kathleen Brooks told AFP.
"That is where investors' fears regarding the single currency are being manifested," adding that risk of intervention by the Bank of Japan to prop up the yen "has just notched up a gear".
However the euro held above $1.29, trading at $1.2958 in the afternoon. On Thursday it had tumbled to $1.2858 -- the lowest since September 14, 2010 -- before rebounding on brighter US economic data.
London's benchmark FTSE 100 index of top companies dipped 0.10 percent to close at 5,572.28 points in a half-day session, ending the year down 5.5 percent.
Frankfurt's DAX 30 added 0.85 percent to close at 5,898.35 points, finishing the year down 14.7 percent.
In Paris the CAC 40 won 0.37 percent to 3,139.25 points in afternoon trading, looking at a drop of around 17.6 percent over the year.
Frankfurt and Paris will reopen on Monday, while London returns for business on Tuesday.
"With traders already gearing up for New Year's Eve, shortened sessions in some regions and no US data in the afternoon, there's little expectation of anything significant happening today," said dealer Jonathan Sudaria at trading group Capital Spreads.
"As traders say goodbye and probably good riddance to 2011 -- a year that saw most of the European and Asian indices recording double-digit losses -- traders may not be so welcoming to 2012 either.
"The one bright spark to 2011 has been the resilience of the United States, given the weak global economic backdrop.
"However, with the European debt crisis still outpacing policymakers' ability to curtail it, and uncertainty over how China's slowdown will land, downside risks are already lining up for 2012."
US stocks slipped lower in opening trade, with the Dow Jones Industrial Average shedding 0.19 percent to 12,264.07 points in the first five minutes.
The tech-rich Nasdaq Composite fell 0.13 percent to 2,610.27 points, while the S&P 500, a broad measure of the markets, dropped 0.15 percent to 1,261.09 points.
In Asia on Friday, equities mostly rose following another set of positive US jobs data, but eurozone debt fears remain after a disappointing debt sale by Italy.
Tokyo gained 0.67 percent to finish at 8,455.35 points, its lowest year-end level since 1982.
The Nikkei index of the Tokyo Stock Exchange finished the year down 17.34 percent, with the March 11 devastating earthquake and tsunami taking its toll on share prices.
Hong Kong meanwhile added 0.20 percent on Friday after a tumultuous year in which it lost a fifth of its value on concerns of a fresh global recession.
Chinese stocks rallied 1.19 percent on Friday, lifted by hopes Beijing may cut bank reserve requirements early next year, dealers said.
However, Shanghai has lost 21.68 percent this year, the biggest annual fall since 2008, on concerns over high inflation, an economic slowdown and tight liquidity conditions, dealers said.