The Sensex at the Bombay Stock Exchange declined 274 points, or 1.6 percent, to 17,363, today, on across-the-board selling by investors, amid weak Asian and European markets. The Nifty at the National Stock Exchange fell 79 points, or 1.5 percent, to 5,280. Stock markets in Japan, China, Hong Kong, South Korea and Singapore dropped between 0.1 percent and 1.4 percent.