* FTSEurofirst 300 down 1.6 pct, bringing weekly loss to 4.9 pct * $300 bln wiped off oil companies' market value since June * Pictet bearish on euro zone stocks for 2015 By Blaise Robinson PARIS, Dec 12 (Reuters) - European stocks tumbled again on Friday, leaving them on course for their biggest weekly loss since May 2012 as shares in oil and oil services firms sank further along with crude oil prices.
The STOXX oil and gas index has plummeted 29 percent since June. The sell-off has wiped roughly $300 billion off market capitalisation of the sector, nearly the size of Denmark's annual GDP.
Saipem dropped 4.2 percent on Friday, hitting a 10-year low, while Royal Dutch Shell was down 2.4 percent, Repsol down 2 percent and CGG down 6.2 percent.
Brent crude fell below $63 a barrel, its lowest since July 2009, as concerns over a global supply glut and a sluggish demand outlook persisted.
Crude has dropped more than 45 percent since June, forcing a number of European oil services companies including Seadrill and Fugro to scrap dividends as oil majors accelerate cost-cutting efforts.
"We're reaching a point where there's a risk of seeing corporate and sovereign defaults in energy-producing countries, which could revive global systemic risks," said Christophe Donay, head of strategy at Pictet, which has $441 billion in assets under management and custody.
"I wouldn't be surprised to see the IMF helping some of the oil-producing countries next year... The key for asset managers for 2015 is really to diversify and hedge portfolios." Pictet has recently sold all euro zone stocks in its portfolios amid doubts about the European Central Bank's ability to revive the region's economic growth, Donay said.
At 1300 GMT, the FTSEurofirst 300 index of top European shares was down 1.6 percent at 1,335.57 points. The index has dropped 4.9 percent so far this week.
It is up 1.5 percent in 2014, well below the 10 percent gain by Wall Street's S&P 500.
Around Europe, Britain's FTSE 100 index was down 1.5 percent, Germany's DAX index down 1.2 percent, and France's CAC 40 down 1.6 percent.
Shares in Danish brewer Carlsberg also featured among the biggest losers, down 4.3 percent as the Russian rouble weakened again. Russia accounts for about a third of Carlsberg's sales.
Europe bourses in 2014: http://link.reuters.com/pap87v Asset performance in 2014: http://link.reuters.com/gap87v Today's European research round-up (Additional reporting by Annabella Nielsen; editing by John Stonestreet)