GLOBAL MARKETS-Stocks, oil fall as investors seek safe-havens

* US new jobless claims unexpectedly jump to 8-month high

* Stocks, oil add to losses after US data

* Treasuries, yen rise as investors seek safe-havens (Updates prices, adds details on commodities sell-off)

By Walter Brandimarte

NEW YORK, May 5 (Reuters) - World stocks fell and crude oil prices slumped on Thursday after fresh data cast more doubts on the strength of the U.S. economic recovery, fueling demand for safe-haven assets.

U.S. crude oil prices plunged more than 3 percent and a benchmark index of world stocks lost 0.8 percent as reports showed weekly U.S. jobless claims jumped to an eight-month high while the country's productivity growth slowed in the first quarter.

For details on the economic reports, see [ID:USJOB=ECI].

U.S. stock indexes opened more than 0.5 percent lower, but the Nasdaq later pared some losses and some economists said seasonal factors related to the Easter holiday may have distorted the jobless claims data.

"I think we're in a situation where the markets and the Fed have been too optimistic," said Bob Andres, chief investment strategist with Merion Wealth Partners in Berwyn, Pennsylvania.

"I don't think we're going to fall off a cliff but the road to real recovery and full unemployment is going to take a long time, and people ought to get back into that mode."

The Dow Jones industrial average <.DJI> was down 102.74 points, or 0.81 percent, at 12,620.84. The Standard & Poor's 500 Index <.SPX> lost 9.00 points, or 0.67 percent, at 1,338.32. The Nasdaq Composite Index <.IXIC> was down 6.29 points, or 0.22 percent, at 2,821.94.

In Europe, the FTSEurofirst 300 <.FTEU3> lost 0.25 percent after falling 1.4 percent on Wednesday on weak U.S. economic data, concern over China's growth outlook and forecast-lagging company earnings.

The MSCI All-Country World index <.MIWD00000PUS> fell 0.8 percent while the MSCI stock index for emerging markets <.MSCIEF> was 0.7 percent lower.

Before this week's decline, world stocks had risen more than 8.0 percent this year on investor confidence in strong corporate earnings and robust growth in emerging markets.

Among the safe-havens benefited by Thursday's data, 10-year U.S. Treasury notes jumped 7/32 in price, the yield at 3.195 percent. The Japanese yen gained around 0.7 percent against the U.S. dollar, at 79.95.

The euro fell against the U.S. dollar after European Central Bank President Jean-Claude Trichet, speaking at a monthly news conference, was less hawkish than some had expected on future rate hikes.

The euro fell to $1.4633 from around $1.4815 after Trichet mentioned upside risks on prices but did not use the phrase "strong vigilance," which traders said suggests the ECB won't hike rates again in June.

COMMODITIES SUFFER

Commodities extended their sell-off into a fourth consecutive day as investors worried about faltering economic growth in major economies and excessive monetary tightening in China, the world's top consumer of raw materials.

U.S. crude oil prices fell 3.75 percent to $105.14 a barrel, while Brent crude lost 3.8 percent to $116.51 a barrel. The decline is the biggest weekly fall for Brent and U.S. crude since the week ended July 4, 2010.

The Reuters-Jefferies CRB index <.CRB>, a global benchmark for commodities prices, dropped 2.6 percent on Thursday. It has lost nearly 6 percent so far this week.

Silver was set for its deepest weekly decline since the late 1980s after the CME Group, in a move to curb speculation, raised margin requirements for the 5,000-ounce COMEX silver futures contract <0#SI:>.

At just below $38 an ounce, silver has fallen around 20 percent so far this week, with investors taking profits from a recent rally that took it to a 31-year high just shy of $50 an ounce.

"I think what's happening is risk aversion across all the asset classes. Everyone thought the U.S. was on a growth trajectory, but now some talk out of the U.S. is showing pretty mediocre growth," said Patrick Armstrong of Armstrong Investment Managers in London.

"We have not been adding any commodity exposure in the dips, but we're still positive on commodities. U.S. dollar depreciation in future will provide a positive tail wind," he added. (Additional reporting by Steven C. Johnson and Angela Moon in New York, Barbara Lewis in London; Editing by Dan Grebler)