While Bagan beat Churchill Brothers 1-0, Dempo defeated ONGC 2-1 in their respective group league matches.
Churchill Brothers put up a stiff fight against Kolkata giants not allowing the latter to take an upper hand till the lemon break with both teams failing to break the deadlock at the Gopal Maidan.
Mohun Bagan, which had defeated Air India 2-0 and drew with Sesa Football Academy in a goalless match, pulled up their socks after the breather and started making forays in the rivals citadel at frequent interval.
With this match, Mohun Bagan are certain to move into the final round with seven points and one more match against Shillong Lajoing FC on Thursday to complete the league engagements.
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Churchill Brothers had two points from two draws and one loss and will play their last league tie against Sesa Football Academy day after.
In another match of Group B, ONGC surged ahead in the 15th minute through a brilliant goal off forward Pawan Thakur, but the team failed to maintain the lead for long.
Dempo's striker Clencio Pinto fetched the equalizer in the 46th minutes while striker Mayon Kaping struck the winner nine minutes later.
Dempo accumulated seven points from two wins and one draw, while ONGC has no points in as many match.