The benchmark indices closed Thursday's trading session on a positive note with Sensex gaining 436.94 points or 0.79 per cent at 55818.11 level, and the Nifty adding 105.20 points or 0.64 per cent at 16628 level. Reliance zoomed 3 per cent to settle at one-month high, thus contributing 68 points to the Nifty gains. Market gains were kept in check with HDFC, HDFC Bank and ICICI Bank qualifying as the main losers.