A Leicester fan was arrested after being involved in an altercation with Nottingham Forest's players in the Reds' stunning 4-1 win over the Foxes in the FA Cup at the City Ground on Sunday afternoon.
In the first game between the East Midlands rivals in eight years, Forest went 3-0 up against the cup holders inside the opening 32 minutes.
After Joe Worrall headed in the Reds' third goal, one Foxes supporter made their way onto the pitch to where the players were celebrating.
The individual briefly managed to become part of the celebratory huddle before being pushed away by Forest's players.
Stewards were quick to react and he was soon tackled to the ground before being taken away by police.
The BBC said on their coverage that the supporter was then arrested and taken to police custody.
Leicester said in a statement: 'The club is appalled by such behaviour and offers its apologies to Nottingham Forest and its players whose safety was compromised.
'We applaud the swift action taken by City Ground stewards in apprehending the individual involved, who will be subject to a lifetime ban from all Leicester City fixtures at home and away.
'We will offer every support to the relevant authorities in pursuing further appropriate action.'
'There were definitely punches thrown and that is disgusting on the football field,' former England defender Jonathan Woodgate said on BBC Radio 5 Live as he described the incident.
'That just should not be happening, it is disgusting.'
It was a sell-out crowd at the City Ground for the FA Cup fourth round tie, with 4,000 Leicester fans making the short trip.
Before the game, police had warned supporters to 'enjoy the game safely'.
Chief Inspector Neil Williams, match commander for Nottinghamshire Police, said: 'Due to Leicester City's recent success, today's match represents the first time these rivals have met in nearly eight years, so I understand that both sets of supporters will want to win.
'While we want everyone who is attending the game to have a great time, it is important that people don't allow their emotions to get the better of them and spoil the day for others.
'Having spoken to fan groups beforehand, we know that the vast majority of supporters will be attending the match just to cheer their side on and to enjoy the feel of another local derby, so our main focus will be to ensure everyone is able to do this safely.'
BelgianDevil
130
Dude displayed more ATTACK on pitch than the Entire Leicester Team
Sabz1916
80
Foxes 🦊 Got LOST In The FOREST 4-1 Reason…Coz They Spent Too much Time in the CITY
Gauzy
40
These type of assholes are not football fans. Respect and Enjoy the game which brings people together.