Extending its losses for the third straight day, the Sensex at the Bombay Stock Exchange declined a modest 23 points, or 0.1 per cent, to close at 19,387, on mild profit-booking, today. The Nifty at the National Stock Exchange fell 10 points, or 0.2 percent, to 5,899.Stock markets in Japan, China, Hong Kong, South Korea and Singapore ended mixed.