Playing in front of 60,000-odd spectators, Pintu Mahata (20th) gave Mohun Bagan the lead, while Ugandan Henry Kisekka doubled the advantage around 10 minutes later.
East Bengal's Costa Rican World Cupper Johnny Acosta (45+2) pulled one back just before half-time with Laldanmawia Ralte (62nd) equalising in the second half which belonged to the red and gold brigade.
The result saw both teams go to 20 points each with Mohun Bagan ahead of East Bengal in the points table on goals scored.
Many people were stranded outside the stadium as the stands were full.
Mohun Bagan were off to a flying start from the word go with Kisekka warming rival goalkeeper Rakshit Dagar's gloves with a curling free kick.
Playing his first Kolkata derby, Acosta had a chance to put the red and golds in front but his header from a long freekick was blocked well by Shilton Paul under Mohun Bagan goal.
The green and maroon brigade were the more dominant side in the opening exchanges, making regular forays inside rival territory.
From one such raid, Mahata fired Mohun Bagan into the lead, turning in a cross from the far post as East Bengal midfielders showed no urgency to track back leaving free spaces inside the box.
Two minutes later, Kisekka almost doubled the advantage with his effort sailing just wide of the target.
Kisekka proved to be a constant menace inside East Bengal's box as Acosta, who played all three group matches in the World Cup in Russia, struggled to keep the Ugandan at bay.
Kisekka got his reward at the half hour mark when his ferocious drive beat Dagar all ends up after East Bengal's Mehtab Singh failed to intercept Arijit Bagui's ball from the right flank.
East Bengal replaced the ineffective Grewal with Lalrindika Ralte in a bid to arrest the slide and at the stroke of halftime, Subhash Bhowmick's wards pegged back riding Acosta's header off a rebound.
East Bengal's performance in the second half was unrecognisable from their colourless first half display.
After the break, Mehtab Hossain -- who ended his long-term association with East Bengal to join Mohun Bagan this season -- was introduced and was in the thick of things immediately.
The experienced midfielder was guilty of a poor touch deep inside his own half with Al Amna lurking and had it not been for a timely save by Shilton, it could have been 2-2.
East Bengal drew level moments later after Laldanmawia Ralte headed in a delightful inswinging corner from Lalrindika Ralte.
Buoyed by the comeback, East Bengal went for the kill as Jobby Justin made a jinking run to into final third to force Shilton into a fine save.
Tempers also flared as players of both teams clashed with Shilton and Al Amna getting exchanged in a verbal duel. Bhowmick threw in tall Bali Gagandeep in place of Justin for the elusive winner. But at the end, both teams had to settle for an entertaining draw.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
