Roberto Martinez scored with virtually the last kick of the game as the defending champions dug deep to fight back from a two-goal deficit to emerge 3-2 winners in a thriller
But the defending champions showed their mettle to pull off a stunning comeback and emerge with a remarkable 3-2 victory, breaking the Young Tigers' hearts and condemn them to a fifth straight loss in the process.
The Stags came into the game on the back of a superb 2-1 away win over Brunei DPMM and were in fine form, being the only side to have won all four of their opening games so far.
But they were handed a rude shock when Akhir Bahari gave the Malaysians the lead with a deflected shot five minutes past the hour mark, before the forward set up substitute Nurshamil Abdul Ghani to make it 2-0 eight minutes later.
Salim Moin's men were heading towards an unexpected defeat and it could have been worse, with both goalscorers unable to add a third as the game crept towards full time.
It was substitute Noh Alam Shah who sparked the comeback as he pulled a goal back in the 85th minute, lashing a low shot beyond goalkeeper Ilham Amirullah for his first of the season.
What followed was an incredible turn of events. Alam Shah again figured crucially as his header was parried into Miljan Mrdakovic's path in the 93rd minute for the Serbian striker to tap home and level,
The last-gasp drama was complete in the sixth minute of stoppage time, when Roberto Martinez headed home Aleksandar Duric's cross to seal a dramatic victory with virtually the last kick of the game.