* Global shares rebound but on track for worst week since June * Gold, oil off lows but remain vulnerable to renewed slide * Dollar gains vs yen on officials' comments to G20 * IBM shares post worst day in 8 years, drags Dow lower By Herbert Lash NEW YORK, April 19 (Reuters) - World equity markets and oil prices rebounded on Friday in a relief rally after a selloff this week that was triggered by signs of sluggish global growth. A lockdown and citywide search for a suspect in the Boston Marathon bombing after another suspect was killed may have contributed to reduced trading volumes but did not appear to have an impact on prices. Brent crude oil stabilized above $99 a barrel in a second day of gains, while stocks on Wall Street and in Europe advanced in a market still rattled by global demand concerns. Stocks sold off earlier in the week on recent weak economic data and a plunge in commodity prices. European indices posted their worst week this year and the U.S. benchmark S&P 500, down 3 percent the past four sessions, was on track to do the same. The S&P 500's close below the 50-day moving average on Thursday indicated the medium-term uptrend in the market could be in peril. The last time the index closed consecutive days under its 50-day average was in early December. Volume was subdued because of this week's selloff and because no U.S. economic data was released on Friday. "A lot of folks in Boston are out of the market and anyone not in Boston is stuck watching the TV trying to find out what's going on there," said Brad Bechtel, managing director at foreign exchange brokerage Faros Trading in Stamford, Connecticut. The market's advance is a reaction to the recent declines more than anything, according to Jack De Gan, chief investment officer at Harbor Advisory Corp in Portsmouth, New Hampshire. "It's a relief rally after the last couple of days," he said. After the selloff, the S&P is still up nearly 9 percent for the year. The pullback could lead investors to reevaluate their positions, said Michael Sheldon, chief market strategist at RDM Financial in Westport, Connecticut. "Unless there's a shock to the system, investors will move back into the market as we head through earnings season, but now investors have an opportunity to study the winners and losers more closely," Sheldon said. The Dow Industrials were pulled lower by a rare quarterly earnings miss from International Business Machines Corp. Three brokerages cut their price targets for the company, whose shares fell 8.1 percent to $190.39, cutting 129 points from the Dow. But some marquee tech names bolstered the broader market and drove the Nasdaq up more than 1 percent, a day after strong earnings from Google Inc and Microsoft Corp. The Dow Jones industrial average was down 24.11 points, or 0.17 percent, at 14,513.03. The Standard & Poor's 500 Index was up 9.54 points, or 0.62 percent, at 1,551.15. The Nasdaq Composite Index was up 35.89 points, or 1.13 percent, at 3,202.25. MSCI's all-country world equity index, which tracks about 9,000 stocks in 45 countries, rose 0.5 percent to 355.76. For the week, the index posted its biggest percentage decline since June. In Europe, the FTSEurofirst 300 of leading regional shares rose 0.5 percent to close at 1,153.19. The index was down 2.4 percent for the week, marred by weaker economic data from Europe's growth powerhouse, Germany, as well as more forecast-lagging data from the United States. The U.S. dollar extended its gains on the yen after Japanese officials in Washington said the global community understands its monetary policy is directed at domestic issues rather than currency manipulation. The euro rose to a session high against the dollar after European Central Bank board member Jens Weidmann said interest rates in Europe are appropriate. The dollar rose 1.54 percent to 99.64 yen, leaving it within sight of the four-year peak of 99.95 yen reached last week. The euro rose 0.11 percent to $1.3064. U.S. stock gains supported a "risk-on" trade in crude oil, sending Brent briefly above $100 a barrel. But worries about global demand and oversupply have kept a lid on the rebound. Brent crude rose 52 cents to settle at $99.65 a barrel. U.S. crude rose 28 cents to settle at $88.01 a barrel. "This remains a market very much driven by the equity markets. They've been rebounding and we're just knocking along with that," said Kyle Cooper, managing director of research at IAF Advisors in Houston. "Crude inventories are at an all-time high, but we're up today," he added. "There are some people who want to believe it's a physical market, but it's not. It's a financial market." The benchmark 10-year U.S. Treasury note was down 6/32 in price to yield 1.7066 percent.