The Sensex at the Bombay Stock Exchange slumped 228 points, or 1.3 percent, to close below the 18,000 level, at 17,998, on Friday . The Nifty at the National Stock Exchange shed 69 points, or 1.3 percent, to 5,409. Other Asian markets in Japan, China, Singapore, Hong Kong and South Korea ended mixed, on continued concerns about global economic growth.