The Bombay Stock Exchange benchmark Sensex gained over 170 points in afternoon trade today and stood at 18,158 a short while ago. Analysts said the rise in Sensex is on the back of renewed buying in banking, FMCG, healthcare and metal stocks.Meanwhile, Japanese shares dropped in early trade today. The Nikkei 225 average was down 1.21 per cent, though most other Asian shares rose. Key benchmark indices in Singapore, South Korea, Taiwan and China rose between 0.12 per cent and 0.78 per cent. Hong Kong's Hang Seng, however, fell by 0.21 per cent.