Celtic will investigate protests outside Parkhead after revealing some players had been left "shaken" after being targeted by missiles from their own fans.
Hundreds gathered to protest outside Celtic Park after a 2-0 League Cup defeat by Ross County - the club's first domestic cup defeat in 36 matches stretching back to April 2016.
Supporters called for the departure of manager Neil Lennon and players also came in for abuse from some fans as they left in convoy in their vehicles amid a heavy police presence.
A Celtic statement read: "Everyone at the club is hugely disappointed by this afternoon's result, one which has ended our phenomenal run of 35 consecutive cup victories.
"While we sincerely share the huge disappointment of all Celtic supporters, there can be no excuse for some of the violent scenes at Celtic Park this evening. The club will be investigating these events fully.
"For players and a management team, who have given so much in recent years and have delivered 11 consecutive trophies, to require an escort from Celtic Park while being targeted with missiles, is simply unacceptable.
"While we understand that only a small number of people were involved in this behaviour, some of the actions this evening, which have obviously left our own players shaken, cannot be condoned in any way."
Abusive chants against Neil Lennon were clearly audible as the under-fire Celtic manager walked into his post-match media conference, as pressure mounts on the former Hoops skipper following a run of two wins in 10 matches.
A police helicopter circled overhead and more than a dozen police vans lined up outside the main stand with a number of other police vehicles parked nearby.
Footage on social media showed some fans kicking down temporary barriers.
"There is an expectation at this club, there's a demand for excellence and there's a demand for wins - I am fully aware of that," said Lennon, who began his second spell in charge of Celtic in February 2019 after Rodgers left for Leicester City.
"I am not standing here like the happy clapper saying everything's okay, because it's not.
"But we'll do everything we can - if I've still got the opportunity to do that - to turn things around."
Australian Associated Press