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Having seen Yang Hyun-Jun's opener cancelled out by Simon Murray's penalty, Iheanacho came off the bench to help Martin O'Neill's side capitalise on Hearts' earlier draw.

League leader Hearts, which was displaced at the summit by Rangers on Sunday (AEST), returned to the top but leads the way by just a point after settling for a 2-2 draw at Livingston.

Celtic took just eight minutes to take the lead through Yang, who reacted quickest to finish from close range after Tomas Cvancara's shot was spilled by Jon McCracken.

Daizen Maeda then forced McCracken into a smart stop with his feet before Cvancara's attempted dink beat the Dundee goalkeeper but clipped the left post in the 31st minute.

But for all of Celtic's dominance, it was pegged back in the 57th minute, when Colby Donovan was adjudged to have blocked Ryan Astley's shot with his hand inside the box.

After a lengthy video assistant referee (VAR) review, referee Steven McLean pointed to the spot, with Dundee captain Murray stepping up and sending Viljami Sinisalo the wrong way.

Yang almost immediately restored Celtic's lead but saw his header tipped over by McCracken, but there was to be one final twist in the final 10 minutes at Dens Park.

Marcelo Saracchi's cross from the left was not dealt with by Astley, with the ball dropping kindly for Iheanacho to smash home on the swivel for his third league goal of the season.

Astley's miserable outing was compounded in the 84th minute as he received a straight red card for a last-man foul on Yang, with Celtic holding on for all three points.