Barcelona will make tickets for European games at the Camp Nou non-transferable, president Joan Laporta said after a reported 30,000 Eintracht Frankfurt fans entered the venue for their Europa League game despite away fans only being allocated 5,000 tickets.
Barca were knocked out of the competition on Thursday by the Germans in the quarterfinals after winger Filip Kostic scored twice in a 3-2 victory that saw Eintracht advance 4-3 on aggregate.
While Barca were expecting huge backing at the stadium, ESPN reported there were close to 30,000 Eintracht fans among the 79,468 crowd.
Of those who attended the game, the club said that 37,746 were season ticket holders, 5,000 tickets were in the away section and 34,440 had bought tickets through other means. The remaining were invited by European soccer's governing body UEFA.
"We insist that the 34,440 tickets that went on sale were tickets restricted to sale outside Germany," the club said on Friday.
"The club did not sell tickets to German fans. Who bought those tickets, did so and passed them on to German fans, that is obvious."
Laporta said Barcelona "is not guilty" for events leading to the tickets ending up in the hands of German fans.
"However, we do assume the responsibility that falls to us," Laporta said.
"We do not want this to happen again at Barca and we will take action: The measures that I can announce and that we have adopted are that for international competition, tickets will be non-transferable.
"The club is not to blame for people breaking the rules, we applied all the measures we could to avoid it," he added.
"But there are people who consider that they have to do it despite the damage to the club and the fans and members who came to support the team at Camp Nou."