DUNDEE UNITED continued their recent run of fine form to send Kilmarnock spinning out of the fourth round of the William Hill Scottish Cup with a 5-2 win at Tannadice.

And sought-after young whizz kid Ryan Gauld provided three assists to further underline his potential.

Andrew Robertson opened the scoring for the hosts, but goals from Darren Barr and Chris Johnston after the break put the visitors into a surprise lead. Stuart Armstrong, though, drew the sides level again before Robertson scored his second of the night to make it 3-2.

And substitute Brian Graham made sure of United's passage into the next round with a well-taken penalty in the 82nd minute after Gauld had been brought down inside the box by Gabriel Reuben, before Gary Mackay-Steven wrapped up the scoring with a blistering 22-yard drive late on.

Kilmarnock began brightly enough, and after 20 minutes Kris Boyd was released by Craig Slater but he could only fire just wide of Radoslaw Cierzniak's near post. The visitors lived to regret not taking that opportunity, though, as United - looking for a third successive win -surged up the park a few minutes later to take the lead in style.

Robertson took a touch to control Armstrong's pass then beat Craig Samson in the Kilmarnock goal from 10 yards out, before Armstrong had another chance with almost the last kick of the first half as the hosts attempted to give themselves some breathing space.

On that occasion, Mackay-Steven went on one of his trademark jinking runs, bursting into the heart of the visitors' penalty area from wide on the right. After leaving two opposing defenders in his wake, he laid the ball back for Armstrong who rather uncharacteristically failed to connect properly. The chance was lost.

Whatever Kilmarnock manager Allan Johnston said to his players at half-time had the desired effect as his side powered ahead within four minutes of the restart.

Firstly, in the 47th minute, they had Cierzniak to thank for coming off his line and missing Craig Slater's free-kick completely. Darren Barr still had to show composure to produce an overhead kick from six yards at the far post, but he did so to give his side an equaliser which had scarcely looked possible going into the interval.

And then - as if that was not enough - the Rugby Park side went one step further by gaining the ascendancy in the 49th minute. There was no slice of fortune this time as Johnston picked possession up from deep. He had only one thing on his mind as he surged towards goal, and the winger made the most of the home team backing off before curling a delightful 20-yard effort high into Cierzniak's top corner.

United had a chance shortly after to get back on level terms, only for John Rankin's shot to be saved by the diving Samson, and though Boyd was still posing a threat for the visitors by keeping the United defence on their toes, it was the hosts who levelled in the 64th minute.

Nadir Ciftci forced his way into the box and looked up to cross for the on-rushing Armstrong, who met it perfectly by applying the finishing touch from close range.

Then, with 15 minutes to go, Robertson made it 3-2 with a low shot from Gauld's through-pass which beat Samson at his near post before Graham and Mackay-Steven completed the rout.