The BSE benchmark Sensex tumbled by 223 points to a nearly three-week intra-day low of 15,658 in early trade today. The 30-share Sensex resumed lower at 15,739 and hovered in a range between 15,795 and 15,655 before quoting at 15,658 at 1015 hours.The sensex was trading 175 points down at 15,705 a short while ago. The NSE's 50-share Nifty index was also down by 62.65 points, or 1.32 per cent, to 4,700.60 in early trade today. It was trading 60 points down at 4703 points a short while ago.