The Sensex at the Bombay Stock Exchange declined 65 points, or 0.4 per cent, to 15,937, in opening trade, this morning, on fresh selling triggered by weak regional bourses. After recovering briefly to gain as much as 131 points at one stage, the Sensex lost ground again, and then moved in and out of the positive zone in very volatile trade, to stand 13 points or 0.1 percent in the positive zone at 16,016 a shortwhile ago.Other key markets in Japan, China, Indonesia, Singapore and South Korea were down by between 0.1 percent and 0.5 percent, today. Across on Wall Street, the Dow Jones Industrial Average had fallen 0.6 per cent, overnight, after the US central bank failed to take any new steps to stimulate growth.