The Sensex at the Bombay Stock Exchange closed with a big loss of 441 points, or 2.4 percent, at 18,008, today. The Nifty at the National Stock Exchange slumped 131 points, or 2.4 percent, to 5,396.The bourses in China, Hong Kong, South Korea and Singapore were closed for a holiday. But the Japanese market gained 1.1 percent.