The Indian equity benchmarks surged on Monday led by gains in country's largest mortgage lender HDFC and the largest private sector lender HDFC Bank after boards of both the companies approved the merger of the two entities in a way paving the way to create the country’s most valuable company, analysts said. The Sensex rose as much as 1,568 points and Nifty 50 index reclaimed its important psychological level of 18,000. Rally in HDFC and HDFC Bank added over 1,000 points towards gain in the Sensex.