Virgil van Dijk has handed in a transfer request to Southampton, claiming he has been "insulted" by the Premier League club.
The Dutch defender, 26, who joined the club from Celtic in 2015 and is a long-term transfer target for Liverpool, insists he is acting after having "numerous" discussions during the past six months about his wish to leave.
Southampton boss Mauricio Pellegrino said last week that Van Dijk no longer wants to play for the club but stressed that the defender is not for sale.
He said he intended to appeal against a club fine of two weeks' wages, that his desire to leave owes to his ambition, and that enquiries from "multiple top clubs have been consistently rebuffed."
A statement released by his management company read: "It is with regret that I can confirm that I have today handed in a transfer request to leave Southampton Football Club.
"Unfortunately I feel I have no alternative after I was given notice of the club's intention to impose a disciplinary sanction against me of a fine equivalent to two weeks' wages. I will be appealing what I feel to be an unjustified sanction and their inability to follow the correct disciplinary protocol in due course.
"Over the past six months I have held numerous discussions with representatives of the board, the former manager Claude Puel as well as the new manager Mauricio Pellegrino to inform them all of my desire to leave the club in search of a new challenge.
"I am incredibly ambitious and want to achieve as much as I possibly can to fulfil my potential in what is a very short career as a professional footballer. I want to play European football again and challenge for major honours and as such I would like Southampton to consider the interest in me from top clubs should it still exist.
"I have been left frustrated by the club's position that I am not for sale and am disappointed that enquiries from multiple top clubs have been consistently rebuffed.
"The period of time that I have just spent injured and unable to play has put a number of things into perspective and made me realise just how important it is to take major opportunities should they arise.
"I have consistently relayed my feelings to senior management at Southampton in what I believed to be private and personal conversations. Disappointingly, these conversations have regularly found their way into the media."
Van Dijk was left out of the club's training camp in France after expressing his desire to leave, but Van Dijk said that it was the club's decision to keep him out of training, not his own.
The statement continued: "I would also like to make clear that I have never once refused to train. I can confirm that I was asked about my frame of mind and for all of the reasons mentioned above I was open and honest in saying that I did not feel I was in a settled mindset given the circumstances.
"Following this conversation the manager explained that he only wanted players who he felt were 100 percent committed to Southampton and told me I would therefore have to train away from the first team.
"As a proud professional I am insulted by the suggestion that it was me who refused to train and so feel it is important to point out the true version of events.
"I had very much hoped to retain the good relationship I've always enjoyed with everyone at the club. Especially the fans, but unfortunately in the light of everything that's happened this has now been seriously affected.
"I would like to make clear that I have nothing but gratitude to everyone at Southampton for giving me the opportunity to play in the Premier League.
"However, the time for me to move on is now and I hope to be able to work with the club to find the best resolution to suit all parties."
Van Dijk joined Southampton for £13 million when his compatriot Ronald Koeman was manager and a year later signed a six-year contract.
After reports emerged in June that he was on the verge of a £60m transfer to Liverpool, Southampton reported them to the Premier League for making an alleged illegal approach.
Liverpool responded by apologising, before also insisting they had "ended any interest in the player."