* Yen touches multi-year lows vs dollar and euro * Nikkei index soars to highest since August 2008 * Asia, European and U.S. stocks improve NEW YORK, April 8 (Reuters) - The yen dropped for a third straight day against the dollar and the euro on Monday as the Bank of Japan began aggressive monetary easing in an attempt to beat persistent deflation, boosting stocks in most markets, though U.S. gains were limited ahead of quarterly earnings reports. The dollar rallied against the yen to its highest level since May 2009, above 99 yen, and the euro touched a three-year peak against the Japanese currency after the BoJ conducted its first bond purchases since announcing the new monetary easing steps last week. Since BoJ Governor Haruhiko Kuroda promised on Thursday to inject about $1.4 trillion into the economy in less than two years, the yen has fallen more than 6 percent against both the dollar and the euro, while Japanese stocks have soared "Barring any sudden spike in risk aversion, (dollar/yen) is likely to roll through that (100) level as momentum remains relentless for the time being," said Boris Schlossberg, managing director of FX strategy at BK Asset Management in New York. The dollar traded at 99.17 yen, up 1.3 percent, while the euro added 2.3 percent to trade at about 129 yen. Japan's Nikkei share average jumped as much as 3.1 percent on Monday to its highest level since August 2008. "The BoJ's bazooka has sparked the buying of Japanese stocks, especially domestic sectors like real estate," said Yasuo Sakuma, a portfolio manager at Bayview Asset Management. The BoJ has said it would buy 1 trillion yen ($10 billion) of government bonds with maturities between five and 10 years, and 200 billion yen of bonds with maturities exceeding 10 years. MSCI's world equity index rose 0.3 percent to 356.50 after registering its worst week of the year on Friday with a five-day loss of 1.26 percent. EQUITY INVESTORS SKITTISH ON EARNINGS Wall Street dipped in early trading as caution ahead of the beginning of the quarterly earnings season dominated sentiment, but stocks turned up moving into the close. But the gains were mostly positioning ahead of what is likely a lackluster corporate earnings season and an economy that could be hitting a slow patch. The Dow Jones industrial average was up 9.83 points, or 0.07 percent, at 14,575.08. The Standard & Poor's 500 Index was up 4.91 points, or 0.32 percent, at 1,558.19. The Nasdaq Composite Index was up 8.20 points, or 0.26 percent, at 3,212.05. Earnings forecasts have been scaled back heading into the first-quarter reports, which kick off this week. S&P 500 earnings are expected to have risen just 1.6 percent from a year ago, according to Thomson Reuters data, down from a 4.3 percent forecast in January. Still, U.S. stocks have rallied this year with major indexes hitting record highs, helped in part by the Federal Reserve's stimulus program. The S&P 500 is up nearly 9 percent for the year so far, while the Dow has gained just under 11 percent. Last week, however, the S&P 500 posted its largest weekly decline this year "We're waiting for earnings for evidence that the market can be supported at these levels," said Jim Dunigan, chief investment officer at PNC Wealth Management in Philadelphia. "We will see growth in earnings, but clearing the expectations bar could be difficult, which could give us reason to pause." European shares rose, led higher by the healthcare sector, as investors tiptoed back into the market, after a sharp drop on Friday on the weak U.S. jobs figures. Traders noted a lack of conviction on Monday -- evidenced by low volumes -- with some investors apprehensive before the start of the U.S. earnings season. The FTSEurofirst 300 closed up 0.2 percent at 1,164.79 points. The euro zone's blue-chip Euro STOXX 50 advanced 0.2 percent to 2,589.25 points. The prospect that Japanese investors will move out of the domestic debt market due to the heavy central bank buying has boosted the attractiveness of some European debt and demand for U.S. Treasuries. The U.S. Treasury 10-year note yield fell sharply last week in response to the new BoJ policy, but edged up on Monday to 1.729 percent as some traders booked profits and dealers prepared for this week's auctions of $66 billion in longer-dated Treasury debt. In Europe the main beneficiary was French debt with 10-year bond yields hitting a record low. CHINA DATA EYED Oil prices were mostly higher, after hitting eight-month lows on Friday on worries over global economic growth. Brent crude rose to a high of $105.55 before trading around $104.72, up 0.6 percent. U.S. crude rose 69 cents to $93.39 a barrel after logging its biggest weekly loss in more than six months last week. A rise in Chinese steel futures to their highest levels in more than a week in anticipation of improving demand in the world's second-biggest economy during the second quarter supported other industrial commodities like copper. Three-month copper on the London Metal Exchange climbed 0.9 percent to $7,471.505 tonne, up from an eight-month low of $7,331.25 hit last week. The metal is still down more than 3 percent over the past three weeks.