Stock markets got a big boost Wednesday after the world's leading central banks joined together to make it easier for banks to get dollars if they need them.

The move by the central banks aimed to ease some of the tensions in global economy, as banks have grown increasingly wary of the fallout from Europe's debt crisis. Banks are afraid to lend to other banks, because no one is really sure how much bad European debt the other holds.

To ease the gridlock, the European Central Bank, U.S. Federal Reserve, the Bank of England and the central banks of Canada, Japan and Switzerland acted to get dollars flowing more freely.

Concerns that another credit crunch is imminent have mounted in recent weeks as Europe's debt crisis has shown alarming signs of spreading to big economies such as Italy and Spain. A default by one or more European governments would lead to severe losses for banks, recession in the United States and Europe and another global credit crunch.

"The joint action is designed to prompt an increase in lending, whilst at the same time reducing some of the strains under which credit lines are currently operating," said Richard Hunter, head of equities at Hargreaves Lansdown. "If the institutions now accept this invitation as intended, a great deal of tension will be removed from the system both in terms of liquidity and market sentiment."

Stocks in Europe had already been buoyed on renewed optimism over the state of the U.S. economy and fresh Chinese policy easing. Sentiment rose despite the failure of European finance ministers to announce radical new measures to deal with the crippling debt crisis afflicting the 17-nation eurozone.

Another round of strong U.S. jobs data Wednesday has also helped shore up hopes about this Friday's U.S. nonfarm payrolls data, which often set the stock market tone for a week or two.

In Europe, an already-strong week gained even more momentum. Germany's DAX was up 4.3 percent at 6,052 while the CAC-40 in France rose 3.6 percent to 3,136. The FTSE 100 index also rose 2.9 percent to 5,489.

The euro also got a lift, trading 1.2 percent higher at $1.3482. Oil benefited too, rising $1.55 a barrel to $101.35.

Wall Street was poised for big gains at the open _ Dow futures were up 2.3 percent at 11,835 while the S&P 500 futures rose 2.8 percent to 1,230.

Markets were also bouyed because China reduced bank reserve levels Wednesday to release money for lending and help shore up slowing growth. Higher growth in China could be crucial for a global economy that's suffering in the wake of the eurozone debt crisis.

The amount of money China's commercial lenders must hold in reserve will be cut by 0.5 percent of their deposits, effective Dec. 5, the central bank said. It was the first easing of monetary policy in three years.

"This is likely to be the first of a series of easing maneuvers from China, though they'll probably unfold over an extended period," said Benjamin Reitzes, an analyst at BMO Capital Markets.

Beijing is gradually easing controls imposed to cool an overheated economy and politically dangerous inflation. Chinese leaders worry that economic growth _ which eased to 9.1 percent in the quarter ending in September from 9.5 the previous quarter _ might fall too abruptly, leading to job losses and possible unrest.

Earlier, Asian stocks closed lower on Wednesday. Japan's Nikkei 225 index dropped 0.5 percent to close at 8,434.61. South Korea's Kospi dropped 0.5 percent to 1,847.51. Hong Kong's Hang Seng dipped 1.5 percent to 17,989.35.

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Nataliya Vasilyeva in Moscow contributed to this report.