The Argentina international, 33,sent a document to the club on Tuesday say he wishes to exercise a clause in his contract, allowing him to leave for free with immediate effect.
Barca were beaten 8-2 by Bayern Munich in the champions league.
Barcelona, though believe the clause has now expired and Messi is contracted to the club untill 2021 with a 700m euro buy -out clause.
The board will meet soon and consider the only thing that could calm Messi is the resignation of the president, Joseph Maria Bartomeu, and early elections.
But Messi seems determined to leave the club no matter what.