Snapping four days of gains, the Sensex at the Bombay Stock Exchange declined 239 points, or 1.3 percent, to close below the 19,000 mark, at 18,802, amid fag-end selling pressure, today.The Nifty at the National Stock Exchange dropped 75 points, or 1.3 percent, to 5,673.Stock markets in Japan, China, Hong Kong, South Korea and Singapore again ended mixed.