Neymar is to fight a claim by Barcelona for compensation following his move to Paris Saint-Germain and has also promised to battle his old club for part of his 2016 contract renewal premium which he claims has not be paid.
Neymar left Camp Nou this month in a world-record €222 million deal, but Barca said on Tuesday they were pursuing damages from the 25-year-old for what they allege to be a "breach of contract."
Neymar's response is the latest move in an increasingly bitter war of words following his move to France.
Neymar and his lawyers released a joint statement, quoted in the Spanish media, which read: "We inform everyone that Neymar and his lawyers are aware of the news released today regarding the legal actions filed by FC Barcelona before the courts of Barcelona.
"Following official notification and after full review of the club's claim, the player's formal defence will be filed in due course.
"Regarding the bonuses owed for the execution of the contract of 2016, it is also necessary to inform that the player has already initiated the formal procedures of collection before the competent courts."
On Monday, Neymar said Barcelona deserved "much more" than the current board of directors and added that it made him "very sad."
On Tuesday, the Catalan club said they were chasing €8.5m in damages with a 10 percent addition and that if Neymar could not pay, PSG should.
The demand appears to relate to a payment made to Neymar when, in 2016, he renewed his contract with Barcelona through to 2021. It was sent to the Spanish football federation on Aug. 11 with a wish for it to be forwarded to the French federation and FIFA.
"Barcelona decided to take these actions in defence of their interests, after a unilateral termination of contract urged by Neymar Jr a few months after signing the renewal until the end of the year 2021," a statement read.
PSG said in response the club were "surprised" by Barcelona's statement.
The Ligue 1 side added in a statement: "The club repeats that, along with Neymar Jr, it strictly respected all applicable laws and rules and can only regret, once again, the attitude of FC Barcelona."
Despite his continuing troubles with Barcelona, life as a PSG player has started well for Neymar, who scored on his debut and then added two more along with three assists in a stunning display against Toulouse on Sunday.
He also posted a series of photos on Instagram alongside former teammates Gerard Pique, Lionel Messi and Luis Suarez among others.