Mumbai, Jul 23 (PTI): The BSE benchmark Sensex surged over 173 points in early trade today extending gains for the fourth straight session on sustained buying by funds amid a firm trend on other Asian bourses.

The 30-share index, which had gained nearly 308 points in the previous three sessions, rose further by 173.38 points, or 0.86 per cent, to 20,332.50 with stocks of banking, IT and sectors leading the rise.

The National Stock Exchange index Nifty gained 51.20 points, or 0.85 per cent, to 6,083.00.

Brokers said sustained buying by funds amid a firming trend in other Asian bourses after weak US data raised the likelihood that the Federal Reserve would keep its stimulus programme in place for some time, influenced the trading sentiment here.

In Asia, Hong Kong's Hang Seng index rose by 0.47 per cent, while Japan's Nikkei by 0.77 per cent in early trade.

The US Dow Jones Industrial Average ended 0.01 per cent higher in yesterday's trade.