UEFA opened a formal investigation into Barcelona last month for potential violation of the European football governing body's legal framework regarding payments made by the club to a company owned by a senior refereeing official.

"I cannot comment directly on this for two reasons," Ceferin told Slovenian newspaper Ekipe SN in an interview published on Monday.

"Firstly, because we have an independent disciplinary committee. And secondly, because I have not dealt with this matter in detail.

"However, I can say something. As far as I am informed, the situation is extremely serious. So serious that it is, in my opinion, one of the most serious (ones) in football since I have been involved in it."

The alleged payments of 7.3 million euros ($7.96 million) were made by Barcelona from 2001 to 2018 to firms owned by Jose Maria Enriquez Negreira, then-vice president of the refereeing committee of the Spanish Football Association.

"At the level of the Spanish league, of course, the matter is out of date and cannot have competitive consequences, while the proceedings are ongoing at the level of the Spanish civil prosecutor's office," Ceferin added.

"The same applies to UEFA, nothing is time-barred here either."

In a statement in February, the club denied any wrongdoing, saying it had paid an external consultant who supplied it with technical reports related to professional refereeing, which it claimed was a common practice among professional football clubs.