Twelve men have been arrested or interviewed under caution following online racist abuse directed at a player in Tottenham's 3-1 home defeat to Manchester United, the Metropolitan Police has revealed.
Although the Met did not confirm the target of the abuse, referring in a statement only to "a high-profile London footballer", Son Heung-min was targeted by trolls during the game in London on April 11.
The South Korea forward was involved in an incident which saw a goal from United striker Edinson Cavani controversially ruled out in the first half, with Scott McTominay adjudged to have fouled Son in the build-up.
Son was subsequently subjected to racist insults both in replies to a tweet from Spurs' official account and in the comments section on his most recent Instagram post.
This abuse was initially detected via United's online reporting tool, and was flagged to police in Manchester, with the Met then taking on the lead for the investigation.
Manchester United have since confirmed six fans, including three season-ticket holders, have been banned for abusing Son on social media and reiterated a "commitment to the fight against discrimination on many fronts".
The Met worked with national policing partners as well as social media companies and both clubs involved to help identify and track down the individuals concerns who made the offensive Twitter posts.
Police activity occurred at a variety of locations across England and Wales over the past two weeks. On Thursday evening, a man was visited by the Met at his home address in Greater Manchester.
Twelve men have each been arrested or interviewed under caution on suspicion of using words or behaviour, or displaying written material with intent to stir up racial hatred.
The Met confirmed each person has been released under investigation as further enquiries continue.
Detective Sergeant Matt Simpson from the Met's public order crime team said: "This action makes it abundantly clear that police will not stand for racist thuggery, even if it is committed online.
"The posts, all of which were on Twitter, were vulgar and were utterly unacceptable.
"There is no safe haven for this type of abusive behaviour and we are committed to taking decisive action to root it out."
Simpson added: "With a busy summer of football approaching we are committed to driving out this type of racist behaviour – it has no place in football.
"I am delighted with the support we have received from our policing colleagues nationally and from Manchester United and Tottenham. Without them, it would be difficult to identify these users and take action."
Chief executive of anti-discrimination body Kick It Out Tony Burnett welcomed the police action.
"We are pleased to see these arrests being made, it sends a powerful message that online abuse is unacceptable and those found guilty will face real-life consequences.
"Social media has become a vehicle for inappropriate behaviour on a societal level and certain people think it's okay to send abusive messages.
"We have to make sure we create an environment where online abuse is punished and that the perpetrators are identified as much as possible.
"These arrests demonstrate the police's commitment to tackling online abuse and we hope this sends a message to others so they think twice before posting discriminatory abuse.
"It's also important that we remain focused on the welfare of those who play, watch and work in football, and receive abuse, and we will continue to offer our support to those who need it."