The Bombay Stock Exchange benchmark Sensex today fell by over 63 points in opening trade on fresh capital outflows by foreign funds. The Sensex, which gained 35.61 points in yesterday's choppy trade, moved down to 16,849.59 in opening trade. The wide-based National Stock Exchange index Nifty also drifted by 21.65 points to 5,020.40. Brokers said fresh selling by funds and retail investors following overnight losses on the US market and weak opening in the other Asian bourses mainly dampened the trading sentiments. Meanwhile,the Bombay Stock Exchange (BSE) and Natrional Stock Exchange (NSE) have announced that they will start trading from 9 AM with effect from tomorrow. The BSE also announced trading in block deal window to 9 AM.