The Sensex at the Bombay Stock Exchange declined 142 points, or 0.8 percent, to close at 18,296, on Tuesday, as concerns about rising oil prices, amid the unrest in West Asia dragged down stock markets across Asia and Europe. The Nifty at the National Stock Exchange fell 49 points, or 0.9 percent, to 5,469.Stock markets in Japan, China, Hong Kong, South Korea and Singapore dropped between 1.7 percent and 2.6 percent.