The Europa Conference League game between Nice and Cologne kicked off almost an hour late after crowd trouble erupted in the stands at the Allianz Riviera stadium in southern France and left one in critical care on Thursday.
Governing body UEFA said the match was "delayed due to crowd disturbance," later adding that it would start at 19.40 local time (17.40 GMT) after TV footage showed supporters of the German team making their way towards the home fans and throwing flares.
Police intervened, but the players had not started warming up shortly before the scheduled 18.45 local time kickoff.
Local authorities said a male Paris Saint-Germain fan was in critical care with head and chest injuries after falling off a stand and 17 others were injured.
"OGC Nice condemns in the strongest possible manner the incidents that took place before the match, which began with damage in the city, followed by the forced entry of dozens of hooligans from the area reserved for Cologne supporters into the presidential stand," the French club said in a statement.
"Stunned by this outburst of violence, even though they had done everything possible to welcome the FC Cologne fans in the best possible conditions, OGC Nice expresses its distress for the Nice public, who witnessed and were victims of these incidents and were forced to wait nearly 45 minutes before being allowed to enter their stadium before kick-off.
The German club said it "condemns every form of violence in the strongest possible terms. We stand for a sporting, fair and respectful behavior with one another. We apologize to all the peaceful fans who had made it a football festival up until this point."
French sports minister Amelie Oudea-Castera said: "I'm fed up. I'm really fed up that our sport is being sullied in this way, that we can no longer say that we are going to a stadium with our children in a serene and secure manner."
Cologne captain Jonas Hector addressed the crowd through the PA system.
"We really want to play the game with you. We also want that game to take place. But we have to say that we do not like to see this," he said.
"We worked damn hard last year and in the playoff. And we would very much like to do this with you and we ask you to keep calm and support us as much as possible."
The match was eventually played and ended in a 1-1 draw.