The Nikkei stock index ended down over 3 percent on Tuesday, extending its losses in afternoon trading, as investors offloaded stocks on concerns over the conflict in the Middle East and surging oil prices.The 225-issue Nikkei Stock Average was down 1,778.19 points, or 3.06 percent, from Monday at 56,279.05. The broader Topix index was off 126.25 points, or 3.24 percent, at 3,772.17.On the top-tier Prime Market, the main decliners were oil and coal product, transportation equipment and nonferrous metal issues.The U.S. dollar briefly strengthened to the mid-157 yen range in Tokyo in a flight…READ FULL ARTICLE