Leicester City complain to the FA about Millwall 'abuse'
Leicester sent a complaint to the Football Association over "abuse, provocation and intimidation" that they claim their fans suffered at Millwall.
The Premier League club say they received "numerous complaints" and will not accept the safety of their "supporters, players, and staff being compromised".
Millwall fans ran onto pitch at the Den on Saturday League One club caused an upset by beating Leicester 1-0 in the FA Cup.
Millwall have said they are "disappointed" the complaint was not made on Saturday.
The FA say they will speak with Leicester City over the issue.
A spokesman for Leicester City said: "We have personally congratulated Millwall on a merited victory and wish them every success in the sixth round."
He added: "However, following receipt of numerous complaints relating to the constant abuse, provocation and intimidation of our players, staff and supporters from our arrival at the stadium, throughout the match and in its immediate aftermath, we have registered our dissatisfaction with the FA. We are awaiting their response."
A Millwall spokesman said: "We have been made aware of these allegations today and are extremely disappointed that Leicester City, as is the professional protocol in such instances, did not raise them on the day of the game itself.
"This morning we received an email from Leicester thanking Millwall Football Club for the hospitality extended to them so are surprised that these serious allegations, which should have been discussed on the day, have come to our attention in the manner they have."