The BSE Sensex which opened 145 points up today, gained 231 points at 17,070 in the afternoon trade on sustained buying by funds and retailers tracking a firming trend in Asian region.Similarly, the National Stock Exchange Nifty moved up by 77points, to 5,177. In the Asian region, Hong Kong's Hang Seng rose by 1.13 per cent, while the Japan's Nikkei by 1.08 per cent in early trade today. The US Dow Jones Industrial Average ended 1.46 per cent higher in the last session on Friday.