U.S. stocks surged more than 2 percent across the board Wednesday, with the Dow and S&P 500 logging their best one-day gains in 2012, as investors bet on more stimulus policies in future.

The Dow Jones industrial average gained 286.84 points, or 2.37 percent, at 12,414.79. The Standard & Poor's 500 was up 29.63 points, or 2.30 percent, to 1,315.13. The Nasdaq Composite Index rose 66.61 points, or 2.40 percent, to 2,844.72.

The broadly increase was because of growing hopes that the central banks around the world, including European Central Bank ( ECB) and Federal Reserve, will implement further measures to support the global economy.

The European Central Bank left its interest rate at 1 percent unchanged, but pledged to extend some of its liquidity providing operations to help financial markets to cope with the ongoing euro zone debt crisis.

Investors expected that ECB will promote more boosting policies in future, given current depressed market situations and slow-down economy in euro zone.

Meanwhile, investors also bet that the Federal Reserve will also boost more monetary policies to beat against market sentiments.

Dennis Lockhart, president of the Atlanta Federal Reserve Bank, said a move to extend the Federal Reserve's Operation Twist program remains an option on the table.

However, some investors bet that Operation Twist program might not be a good choice as the central bank has already had too many long-term treasury bonds on its balance sheet. They bet that the Fed might boost the third round of Quantitative Easing Program, known as QE3.

On economic front, The Federal Reserve said in its beige book that U.S. economy "expanded at a moderate pace" from early April to late May. The central bank said the world largest economy saw rising factory output, improving real-estate and steady or slightly increased hiring.

The beige book was prepared for the monetary policy meeting scheduled on June 19-20. Fed's officials will give clearer statements of U.S. economic situation in the coming days, with Fed Chairman Ben Bernanke testifying before Congress about the economy on Thursday.

As for other markets, the U.S. dollar fell against major currencies in late New York trading on Wednesday as the euro rebounded on ECB president's implication of further easing policy. The dollar index lost 0.534 to 82.379 on Wednesday.

Crude prices rose for the third straight day on Wednesday as hopes for European Central Bank's more supportive measures boosted market sentiment.

Light, sweet crude for July delivery rose 73 cents, or 0.86 percent to settle at 85.02 dollars a barrel on the New York Mercantile Exchange. In London, Brent crude for July delivery gained sharply by 1.80 dollars, or 1.82 percent to close at 100.64 dollars a barrel.