Kyle McAllister scored the deciding spot-kick as St Mirren beat Kilmarnock 5-4 in a penalty shootout to book a place in the semi-finals of the Scottish Cup, after the match had ended 3-3 after 120 minutes.

On a dramatic night, a mistake by Killie keeper Colin Doyle in the 25th minute at Rugby Park allowed a harmless cross from Ilkay Durmus to go through his hands.

However, the visitors failed to capitalise on their good fortune and a header from loan defender Zeno Ibsen Rossi in the 36th minute and a Greg Kiltie strike just before the break gave the hosts the interval lead.

Kilmarnock, without injured in-form striker Kyle Lafferty, had several chances to go further ahead but with six minutes remaining Buddies skipper Joe Shaughnessy headed in a dramatic equaliser to set up extra time, where Killie played a big chunk of it with 10 men after substitute Nicke Kabamba limped off with the Ayrshire side having used all four substitutes.

However, Ross Millen scored from the spot in the 101st minute and Jamie McGrath did likewise to set up a penalty shoot-out.

Saints keeper Jak Alnwick made the only save from Rory McKenzie, Killie's second, as Gary Dicker, Mitch Pinnock, Millen and Aaron Tshibola scored with McGrath, Cameron MacPherson, Colin Quaner, Joe Shaughnessy and McAllister making no mistake for the Paisley side to end the drama.

The game only really came to life in the 25th minute when visitors were gifted the lead.

As a line of players from both sides spread themselves along the Kilmarnock penalty area in anticipation of a free-kick,  McGrath played Durmus down the right.

The midfielder clipped a cross into the box which looked easy for Doyle but somehow the 35-year-old on-loan Hearts keeper allowed the ball to slip through his hands and over the line.

Killie shook themselves out of their dismay.

There was a penalty claim when Shaughnessy challenged Lafferty's replacement George Oakley for a Chris Burke cross, bundling him to the ground, but referee Don Robertson pointed only for a goal kick.

However, the home side were soon level when Burke's corner from the left was headed in by Bournemouth loanee Ibsen Rossi, his first goal for the Premiership club.

A minute before the break the cup tie turned in Killie's favour when Oakley set up the unmarked Kiltie and from 14 yards fired a low drive past Alnwick and in off the far post.

Millen's header from a Pinnock corner was headed off the line by Jake Doyle-Hayes before Alnwick tipped a shot from Kiltie over the bar, saving Kirk Broadfoot's header from the corner.

Oakley flicked a Kiltie cross over the bar and Doyle made a save from a Marcus Fraser header before Saints levelled.

McGrath's delivery from a free-kick was headed in from six yards by Shaughnessy and the Buddies would have snatched it near the end of normal time had Doyle not made a great close-range save from substitute Quaner.

Killie substitute Kabamba limped off soon into extra time and, having already used their four replacements, the home side had to soldier on with 10 men.

And when referee Robertson judged that Saints substitute McAllister had fouled Brandon Haunstrup inside the box, Millen stepped up to beat Alnwick.

Saints levelled again, also with a penalty, when Doyle felled Doyle-Hayes with McGrath converting and Doyle's last-gasp save from Shaughnessy's header ensured a penalty shoot-out where the Buddies came out on top