The Sensex at the Bombay Stock Exchange rose 113 points, or 0.6 per cent, to regain the 18,000 point level, at 18,107 in opening trade Tuesday morning, on fresh buying by investors. Later, after paring its gains somewhat, the Sensex stood 79 points, or 0.4 percent in positive territory, at 18,073 in afternoon deals, a short while ago. Stock markets in Japan, Taiwan, South Korea, China and Hong Kong were trading mixed on Tuesday. The US Dow Jones Industrial Average had lost 1 per cent, overnight.