Celtic progressed to the Scottish Cup semi-finals after edging past Rangers 4-2 on penalties following a tense 0-0 draw at Ibrox on Sunday.
However, the game ended in ugly scenes as supporters from both sides invaded the pitch after the shoot-out.
The quarter-final had been tightly contested but lacking in quality for long spells before the drama unfolded from the penalty spot.
Rangers had looked the more threatening side throughout the 120 minutes and created the majority of the chances in front of their home crowd.
However, the hosts were unable to convert their pressure into a decisive goal.
Celtic, missing several key players through injury, were forced into a largely defensive display and spent long periods absorbing sustained pressure from Rangers.
The visitors thought they had taken the lead during the first half when Daizen Maeda powered a header into the net.
The goal was eventually ruled out following a VAR review that confirmed an offside in the build-up.
Rangers pushed harder after the interval and continued to dominate territory as Celtic struggled to retain possession.
Several promising openings came and went for the home side as they searched for the breakthrough.
Viljami Sinisalo produced a number of composed moments in the Celtic goal while defenders repeatedly threw themselves into blocks inside the penalty area.
The hosts thought they had finally found the winner during extra time when Emmanuel Fernandez bundled the ball into the net from a corner.
That effort was also ruled out after the referee judged that the ball had struck the defender’s hand before crossing the line.
Despite finishing the match with 24 attempts on goal, Rangers were unable to find a way past Celtic’s determined defensive line.
With neither side able to break the deadlock, the tie was decided by a penalty shoot-out.
James Tavernier struck the crossbar with the opening kick to immediately put the hosts under pressure.
Djeidi Gassama then fired his penalty over the bar to leave Rangers facing an uphill task.
Celtic converted all four of their penalties with composure.
Tomas Cvancara delivered the decisive kick to send the visitors into the semi-final draw.
Celebrations quickly spiralled into disorder when Celtic supporters rushed onto the pitch following the winning penalty.
Rangers fans soon followed, leading to chaotic scenes as stewards and police attempted to separate the two groups.
Missiles and flares were thrown during the disturbance.
Order was eventually restored, although the incidents are likely to face further scrutiny.
The Scottish Football Association later confirmed that an investigation will be launched into the events that followed the final whistle.
While Celtic advanced to the last four of the Scottish Cup, the dramatic quarter-final will be remembered as much for its chaotic ending as for the result.
