Snapping three days of gains, the Sensex at the Bombay Stock Exchange closed with a marginal loss of 15 points, or 0.1 percent, at 16,451, on mild profit-booking, today. The Sensex had gained 428 points in the previous three trading sessions. The Nifty at the National Stock Exchange dropped 12 points, or 0.2 percent, to 4,956. Stock markets in Japan, China, Hong Kong, South Korea and Singapore ended mixed.