A second-half hat-trick from Leigh Griffiths gave Celtic a comfortable 3-0 win over Dundee United at Tannadice Park and increased their lead at the top of the Scottish Premiership to eight points with four games to play.

Virgil van Dijk powered a header from a Stuart Armstrong corner over the top early on, before Robbie Muirhead's speculative strike from range was beaten away by Craig Gordon at the other end.

The lively Emilio Izaguirre cut his way through the Dundee United right on the half-hour mark before pulling the ball back to the waiting Van Dijk, who could only hammer his effort straight at Radoslaw Cierzniak from 12 yards.

The major talking point of the first half came just moments later when referee Willie Collum elected to only book Scott Brown for his feisty tackle on John Rankin, when many of the crowd felt a red would have been more appropriate.

To the home side's annoyance, Brown was then involved in the opener just two minutes after the restart as he picked out Stefan Johansen on the edge of the Dundee United box, who in turn played in Griffiths to take a touch before firing hard and low past Cierzniak.

Cierzniak then reacted smartly to paw away a goal-bound Kris Commons header, before making another good stop from Johansen's 20-yard strike on the hour.

However, the goalkeeper was powerless to keep out Griffiths's tap in from just a yard out, after Callum Morris had headed the ball against his own post from a Celtic corner.

In an exciting late cameo, substitute Gary Mackay-Steven thumped an effort against the bar and then won a penalty when he was brought down, although replays showed that the foul may have taken place outside the area.

Commons, Celtic's normal penalty taker, then handed the ball to Griffiths, who made no mistake from the spot to grab his hat-trick and seal the win.