* FTSEurofirst 300 rises 2.1 pct, biggest gain in 3 months
* Spanish banks rebound strongly
* Miners among top gainers; China factory output data helps
* Carrefour falls 5.6 percent after cutting forecast again
By Brian Gorman
LONDON, Dec 1 (Reuters) - European shares posted their biggest one-day gain in three months on Wednesday, buoyed by better-than-expected U.S. labour data, and with miners gaining on strong factory output numbers from top metals consumer China. The FTSEurofirst 300 index of top European shares rose 2.1 percent to close at 1,089.16 points, the biggest one-day percentage gain since Sep 1.
The index fell to an eight-week closing low in the previous session on worries about euro zone sovereign debt.
Spain's two biggest banks, Banco Santander and BBVA, were among the standout risers on Wednesday, up 7.2 and 7.3 percent respectively, regaining some of the ground lost in recent days.
Other banks to gain included Lloyds and UniCredit, up 6 and 6.5 percent respectively. Greek banks rose 7.7 percent.
Some strategists put the index's surge down to bargain hunting. "Some stocks were getting cheap. People have just had a chance to reflect on some of the corporate earnings we've had this year," said Mark Webster, head of European active equities at State Street in London.
"My sense is that people are still looking to buy on weakness rather than sell into strength."
U.S. private sector payrolls saw their biggest rise in three years in November, lifting optimism about the jobs market ahead of Friday's key government employment report.
Adding to the view that the U.S. economic recovery was picking up steam, non-farm productivity grew faster than previously estimated in the third quarter.
Figures showed China's official purchasing managers' index (PMI) rose to a seven-month high in November.
Metals prices, also boosted by a weaker dollar, rose. Miners to gain included BHP Billiton, Rio Tinto and Xstrata, up between 3.1 and 5.8 percent.
A bailout for Portugal "is in the price", Webster said, "and the reaction would be relatively muted. We may get a year-end rally with some optimism for 2011".
But other analysts said the market bounce may be short-lived and concerns over euro zone debt could soon resurface.
"Today is a good day but I would not bet on this lasting for too long. We still have considerable uncertainties around the sovereign credit crisis and this will, on and off, spook the market," said Klaus Wiener, head of research at Generali Investments in Cologne.
Analysts also said the market got support from technical buying after shares moved closer to an oversold territory.
Britain's FTSE 100, Germany's DAX and France's CAC 40 ended the day between 1.6 and 2.7 percent higher, while the Thomson Reuters Peripheral Eurozone Countries Index rose 4.3 percent. Spain's IBEX rose 4.4 percent.
CARREFOUR CUTS
French retailer Carrefour fell 5.6 percent after cutting its 2010 profit forecast for a second time in six weeks..
Volvo rose 6.2 percent after UBS raised its rating on the Swedish truck maker to "buy" and after a reweighting of indexes.
Other auto makers gained, helped by an upbeat Nomura note saying the continent's market should be "back in the black in 2011". Renault and BMW rose 5.1 percent.
British insurer Prudential rose 5.5 percent after outlining a plan to double Asian new business profits.
The Euro STOXX 50 rose 2.7 percent, moving back towards a key support level -- the 50 percent retracement of the index's drop from an April high to a May low.
Wall Street was higher around the time European bourses were closing. The Dow Jones, S&P 500 and Nasdaq Composite were up between 1.8 and 2 percent. (Additional reporting by Atul Prakash; Editing by David Hulmes)