Flares were thrown on the pitch and fighting broke out in the Croatian end during their 2-2 Group D draw with the Czech Republic - leaving them likely to face UEFA sanctions.
Referee Mark Clattenburg was forced to stop the game with four minutes left while a steward was almost hit by a firecrakcer, along with Croatia goalscorer Ivan Perisic.
It forced 10 minutes of stoppage time, allowing Tomas Necid to score a late penalty and snatch an unlikely draw after the Czech Republic were outplayed for 75 minutes.
The violence was condemned on Twitter.
-- Samuel Aston (@ThePathOfAMedic) June 17, 2016
Are certain fans never going to learn how to behave?!? There is NO place in sports for crowd violence, fighting or flares! #CZECRO
-- Martin Johannessen (@m_johannessen) June 17, 2016
More disgusting scenes, play stopped after flares thrown on pitch and fans fighting in stands. You are winning you idiots. #CZECRO
-- Lynsey Hipgrave (@lynseyhipgrave1) June 17, 2016
Many wondered if security should have done more.
Doesn't give one much confidence in French security if these supporters can smuggle in flares. What else could they bring in? #CZECRO
-- Damien Stenson (@Damienstenson) June 17, 2016
The euros are genuinely out of control. Considering France is on 'high alert' its shocking the amount of flares have gone off #CZECRO
-- Zachary (@Kyozarok) June 17, 2016
Croatia boss Ante Cacic told a press conference: "These people are really scary, that is why I call them hooligans. These are not really Croatian supporters. These are sports terrorists. The main thing our country doesn't want to mess with, this kind of hooligans.
"This is maybe just a question about six to 10 individuals. I hope they can be identified and punished. I hope the Croatia FA is doing everything to prevent this but it is impossible to avoid."
He added: "Ninety-five percent of our supporters are ashamed in front of Europe, the players are very sad that after playing a beautiful match this happens."