Barcelona president Joan Laporta says the club will change its ticket policy for European games after around 30,000 Eintracht Frankfurt fans gained entry to Camp Nou for Thursday's Europa League game.
Frankfurt were given 5,000 tickets for the game by Barca but thousands more secured seats in the home end to see their team stun Barca 3-2 and book their place in the semifinals of the competition.
Laporta said he was "ashamed" by the scenes in the stands and promised that the club was already working on ensuring there will be no repeat in the future.
"We feel really bad, it was shameful," Laporta told Barca's website on Friday. "I am appalled by the image presented and feel ashamed as this should never have happened.
"The club is not guilty regarding events leading to the tickets ending up in the hands of German fans. However, we do accept the responsibility that falls on us.
"We do not want this to happen again at Barca and we will take action: the measures that I can announce for now -- and that will be adopted for all international competitions -- is that tickets will become non-transferable.
"It is something we never wanted to do because it is inconvenient for fans who follow the rules. But we have no option to ensure that what happened against Frankfurt does not happen again."
Laporta insisted that the club did everything it could to avoid away fans purchasing tickets, including blocking German IP addresses and credit and debit cards buying from the online ticket office.
The attendance at Camp Nou on Thursday was just under 80,000. Of those present, around 38,000 were season ticket holders, 5,000 were in the Frankfurt section and another 34,440 had bought tickets for the match through other means.
"We insist that the 34,440 tickets that went on sale were restricted to sale outside Germany," Laporta protested. "The club did not sell tickets to German fans. Those who bought those tickets passed them on to German fans, that is obvious."
Just two weeks ago, Barca made a plea to season ticket holders who were not able to attend matches to return their tickets to help the club in two ways: financially through resale and by improving the atmosphere at Camp Nou.
In the week leading up to the game, though, prices for Frankfurt's visit rose to between €150 and €300, with many local supporters telling ESPN they felt priced out of attending.
Barca's ultras -- the supporters who occupy the stand behind one of the goals -- boycotted the first 10 minutes of the second half in protest at so many Frankfurt fans gaining access to the home end.
Speaking to Cadena Ser on Friday, vice president Elena Fort said Barca had made around €3 million in ticket revenue from the fixture, although the profit had "left a bad taste."
Barca coach Xavi Hernandez was also furious after the game, saying the atmosphere "did not help" and that he and the players wanted an explanation from the club about what had happened.
A source close to the dressing room told ESPN the Barca players were "shocked" by what they saw when they went out to warm up, with thousands of Frankfurt fans jeering them and creating a hostile environment in their own ground.
Despite the security risks of the fans mixing, though, the game passed without any major incidents, although Barca did apologise to supporters who they said suffered "anti-social behaviour" from the visitors.
"The club is deeply sorry for the tense atmosphere experienced due to improper behaviour by some German fans and it wishes to give its support to all those Barca fans who felt intimidated by the anti-social behaviour," a statement added.