They are currently ranked 10th in the table with 24 points from 21 games, while Punjab FC has slipped down to the 11th position.
With three games left to play, both East Bengal and Punjab FC are eight points behind the sixth-placed Mumbai City.
East Bengal made some promising moves from the left flank to start the game, while Punjab FC's backline were alert to the danger in the early exchanges.
The Red and Gold brigade took the lead when their Greek forward hammered a shot on goal from the left, more in hope than conviction but it went through Ravi Kumar's legs into the goal.
Diamantakos had another opportunity to double the lead in the 44th minute when Raphael Messi Bouli found him with a low cross after beating his marker.
However, before the 31-year-old could get his shot away, Ivan Novoselec stole the ball from his path and averted the danger.
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Panagiotis Dilmperis made two attacking changes at the start of the second half. He introduced Luka Majcen and Nihal Sudeesh, replacing Asmir Suljic and Asish Pradhan respectively.
However, Punjab FC were caught ball-watching as Mahesh slotted the ball past Ravi in the goal to extend the lead for the visitors.
It all started from a long throw for East Bengal where Messi Bouli shrugged off his marker and released a cross to Vishnu in space. His shot was blocked by Novoselec but it landed kindly for Mahesh, who calmly nestled it into the back of the net.
The Red and Gold found the third goal from Mahesh's corner which was initially punched away by Ravi but Punjab FC defenders were unable to clear their lines.
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Lalchungnunga showed great awareness in finding the bottom corner with a thunderous strike.
In the 61st minute, Punjab FC almost scored when Khaiminthang Lhungdim found Majcen with a long pass and the Slovenian headed it towards goal.
But Prabhsukhan Gill was alert to the danger and showed great reflexes to keep out the header.
A minute later, the hosts eventually scored when a scrappy cross from the right bounced near East Bengal's final third.
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It was Vidal, who reacted first and volleyed the ball into the top corner, leaving Gill and the defenders in awe.
(Except for the headline, this story has not been edited by staff and is published from a syndicated feed.)