The Sensex today surged by 273 points to a six-week high on fund-based buying in blue-chips, particularly Reliance group stocks. The 30-share index shot up by 273 points to 17,338 points. The broad-based National Stock Exchange index Nifty spurted by 78 points to 5,198 points. The market sentiment boosted after Reliance Industries, the most valuable company, climbed to its highest in a month on agreeing to take control of Infotel Broadband Services, giving it access to the wireless Internet business.