The BSE Sensex shot up by more than 590 points in opening trade today, while the NSE Nifty regained the 5,000 points level on the back of a firming trend in global markets after coordinated action by central banks to pump liquidity into the financial system.The 30-share BSE Sensex index, which had gained 115.12 points in the previous session, rallied by another 590.91 points, or 3.66 per cent, to 16,714.37 within minutes of the opening bell today.In a similar fashion, the wide-based National Stock Exchange Nifty index rose by 172.80 points, or 3.58 per cent.