NEW YORK, June 15 (Reuters) - Wall Street extended gains in late afternoon trade on Friday on hopes of collective action from global central bankers if the closely watched election in Greece this weekend results in market turmoil. The Dow Jones industrial average was up 94.90 points, or 0.75 percent, at 12,746.81. The Standard & Poor's 500 Index was up 10.80 points, or 0.81 percent, at 1,339.90. The Nasdaq Composite Index was up 30.49 points, or 1.07 percent, at 2,866.82.