Barcelona has paid 13.5 million euros ($18.53 million) to the Spanish treasury after the club was charged last week with tax fraud in the signing of Brazil forward Neymar.

The Spanish champion reiterated that it did not consider it had committed any offense and said it had made the payment due to a "possible difference of interpretation" about how much it owed after signing Neymar in the close season.

Club president Josep Bartomeu said Barca would fight to defend itself "because we are in the right", and expressed surprise the case had blown up so quickly.

Barca members, or socios, who own the Catalan club, had no reason to be concerned, he told a media conference after a board meeting on Monday.

"It is very strange," he said. "Everything is going very fast and we do not know why. The Barca members should be satisfied with what we have explained - it is the truth."

The exact amount transferred to the public coffers was 13,550,830.56 euros, Barca said on its website, meaning the club has now paid just short of 100 million euros ($132 million) to secure the player's services.

The aim of the payment was "to cover any potential interpretation made concerning the contracts signed in the transfer process for Neymar, although we remain convinced that the original tax payment was in line with our fiscal obligations", the club said in a prepared statement.

"As we have done so far, the club will continue to give maximum collaboration to the law courts in order to clarify the facts of the case.

"The board again insists that in relation to this signing, the club has scrupulously fulfilled its fiscal obligations in line with its awareness at the time of the contracts and agreements signed in good faith."

It was not immediately clear whether the payment would mean the fraud charges laid by a Madrid court would be dropped.

Barcelona was forced on the defensive over the deal after a member filed a complaint against Bartomeu's predecessor, Sandro Rosell, alleging misappropriation of funds.

Rosell, who denied any wrongdoing, stepped down saying he wanted to protect the club's image. But when details of Neymar's signing came to light the judge overseeing the case granted the public prosecutor's request to lay charges for tax fraud.

After Rosell's exit, Barca admitted Neymar had cost 86.2 million euros, including payments to the player and his family, and not 57.1 million as it originally said.

Together with Monday's payment to the treasury, Neymar has cost the club almost as much as the record $135 million arch-rival Real Madrid paid for Wales winger Gareth Bale last year.