Building on early gains, the Sensex at the Bombay stock Exchange zoomed 383 points, or 2.1 per cent, to 18,733 in afternoon trade, today. At one stage, the Sensex had posted its biggest single-day intra-session gain this year, of 464 points. Earlier in the morning, the Sensex had opened 149 points, or 0.8 per cent in positive territory, at 18,498. The Sensex rallied, as the market cheered the government's notification of its decision on Foreign Direct Investment in multi-brand retail, and some other sectors, and as regional markets rose.Key stock indices in Japan, China, Hong Kong, Indonesia, Singapore, South Korea and Taiwan were up by between 0.2 percent and 0.8 percent, today. The US Dow Jones Industrial Average had ended 0.1 per cent higher in yesterday's trade.