Celtic came from behind to win 4-3 at Hearts and extend their lead at the top of the Scottish Premiership to four points as Rangers were held 1-1 at home to Livingston.

VAR made an explosive introduction to Scottish football at Tynecastle where Hearts striker Lawrence Shankland finished on the losing side despite scoring a hat-trick.

In just the second Premiership game to use the technology, Shankland scored twice from the penalty spot either side of putting Hearts 2-1 in front early in the second half.

But goals from James Forrest, Giorgos Giakoumakis, Daizen Maeda and Greg Taylor gave the champions all three points.

Celtic boss Ange Postecoglou said ahead of the game his wish was for VAR not to intervene at all, but the Australian was left disappointed as he laughed and sarcastically applauded a series of first-half decisions.

Celtic went in front on just 14 minutes when James Forrest headed in Anthony Ralston's cross.

Shankland had started the game on the bench but made an early introduction to replace the injured Stephen Humphrys.

The Scotland international was given the chance to equalise after a VAR review for Cameron Carter-Vickers' challenge on Cammy Devlin and slotted past Joe Hart.

Celtic thought they too should have had a penalty before the break, but this time VAR did not recommend a review for a handball by Michael Smith.

"I thought we had a clear-cut handball and penalty but apparently that's not good enough," said Postecoglou.

"We haven't had a penalty all year and I keep hearing opposition managers saying we get everything. The only penalties we have taken so far this season have been in training."

Just 90 seconds into the second half, Shankland turned home Josh Ginnelly's low cross from close range.

Celtic roared back as Giakoumakis headed in from a corner before Maeda forced home the rebound after Craig Gordon parried Aaron Mooy's shot.

Hearts were then awarded a second penalty for a foul on Devlin.

Shankland saw his effort saved by Hart and miskicked his follow-up but Ginnelly raced in to knock home.

However, VAR ordered a retake after the winger and Moritz Jenz were shown to be encroaching and Shankland sent Hart the wrong way.

Postecoglou immediately sent on Sead Haksabanovic, Liel Abada and Taylor in the search for a winner.

And it was the left-back who was the unlikely hero as he stabbed home Abada's deflected shot for his first league goal for Celtic in 61 games.

Celtic's day got even better after Rangers could only take a point against 10-man Livingston.

The visitors were on course for their first ever victory at Ibrox thanks to Joel Nouble's fourth-minute goal.

VAR was also involved when Livi were reduced to 10 men 12 minutes from time for Morgan Boyes' challenge on Alfredo Morelos, which was upgraded from a yellow to a red card.

John Lundstram saved Rangers' blushes when he volleyed in Ryan Kent's cross in the 91st minute.

But the final whistle was met with a chorus of boos with the pressure increasing on Rangers boss Giovanni van Bronckhorst.

Aberdeen are up to third after a 2-1 win at Motherwell, while St Mirren were also 2-1 victors over Dundee United to move into fourth.