The Sensex at the Bombay Stock Exchange surged 354 points, or 2 percent, to close above the 18,000 level after more than six months, at 18,202 on Wednesday.The Sensex rose on sustained buying by funds, on hopes that easing inflation will lead to lower interest rates, and amid rising Asian and European markets.The Nifty at the National Stock Exchange jumped 116 points, or 2.1 percent, to 5,532.Stock markets in Japan, China, Hong Kong, Singapore and South Korea gained between 0.8 percent and 2.3 percent.