Celtic captain Callum McGregor scored a 95th-minute winner as Martin O'Neill's side battled to a 1-0 win over St. Mirren in the Scottish Premiership.

The Bhoys looked likely to lose further ground on leaders Hearts as they failed to muster a shot on target until second-half stoppage time, but McGregor's thunderous strike broke St. Mirren's hearts at the death.

St. Mirren made Celtic uncomfortable from the off, with Conor McMenamin prodding just wide in the early stages then firing off a long-range effort that clipped the far post.

The first shot on target from either team did not arrive until the 64th minute, when Keanu Baccus curled straight into Kasper Schmeichel's gloves, though the ball was in the Celtic net five minutes later.

Liam Scales prodded a bouncing ball past his own goalkeeper, but the goal was disallowed due to McMenamin interfering with play from an offside position, with the decision being confirmed following a VAR review.

It looked like the game was meandering towards a goalless draw when Schmeichel denied Declan John at his near post, but deep into stoppage time, McGregor sent a left-footed thunderbolt arcing into the top-right corner from distance to spark wild celebrations.

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McGregor's stunning winner came from Celtic's second shot on target, with the champions playing 93 minutes before first testing Shamal George in the St. Mirren goal.

But one wonderstrike was enough to move them within four points of leaders Hearts, who visit Aberdeen on Sunday.

Across his two spells in charge of Celtic, O'Neill has won all five of his games against St. Mirren without conceding a single goal.

He is just the sixth Celtic boss to achieve that feat against any opponent, after Jock Stein against Airdrieonians, David Hay against Clydebank, Liam Brady against Dundee, Neil Lennon against St. Mirren, and Ronny Deila against Partick Thistle.