Mohun Bagan rode on Odafa Okolie's strike from a penalty to edge East Bengal 1-0 in their round 6 I-League fixture at the floodlit Yuba Bharati Krirangan in Kolkata on Sunday.
Okolie fired in from the spot in the 22nd minute for the decisive goal in a match that had more than 85,000 frenzied supporters in attendance.
But in an embarrassment for the organisers, play had to be stopped for 18 minutes in the second-half with yet another power cut in the 1,20,000 capacity stadium, something that broke the tempo of the match.
Mohun Bagan now have 15 points from six matches, while East Bengal remained on 10.
Playing without their inspirational playmaker Mehtab Hussain and in-form forward Tolgay Ozbey, East Bengal were better in ball possession in the first 45 minutes, but they lacked creativity to take an upper hand.
Mohun Bagan, on the other hand, held their nerves, even as East Bengal played a physical game that led to a penalty in the 20th minute.
The burly East Bengal defender Uga Okpara brought down a surging Sunil Chhetri from behind inside the box and referee Pratap Singh awarded a penalty in favour of Mohun Bagan.
Odafa converted from the spot, getting past Gurpreet Singh with a swift right-footer to give Mohun Bagan 1-0 lead.
But Mohun Bagan failed to capitalise on the lead even as East Bengal intensified their attack especially after the changeover.
Churchill edge Mumbai FC 1-0
Henry Arnaud Autchouet's penalty strike in the first half propelled Churchill Brothers to a solitary goal win over Mumbai FC in their sixth I-League match at the Nehru Stadium, Fatorda, in Margao on Saturday.
Autchouet, who received the ball inside the box attempted to take a shot which Keegan Pereira handled and referee Balasubramaniam pointed to the penalty after showing a yellow card to the Mumbai FC player. Autchouet converted the penalty to the joy of his teammates.
The victory takes Churchill, who won their fourth match, to 13 points from six matches, while Mumbai FC who lost their fifth match remained on three points from six matches.