Manchester United striker Marcus Rashford said "people are hurting and people need answers" after the death of George Floyd, the US African American man who died in Minneapolis after a white policeman knelt on his neck.
Floyd's death on May 25 has sparked unrest and the imposition of curfews in dozens of cities across the US, while in London on Sunday a demonstration was held in support of the #BlackLivesMatter movement.
"At a time I've been asking people to come together, work together and be united, we appear to me more divided than ever. People are hurting and people need answers," Rashford posted on his Instagram account.
"Black lives matter. Black culture matters. Black communities matter. We matter. #justiceforgeorgefloyd #justiceforahmaudarbery #justiceforbreonnataylor."
Rashford's United colleague Paul Pogba also joined the calls and revealed his sadness on his Instagram account.
He wrote: "During the past few days I have thought a lot about how to express my feelings about what happened in Minneapolis. I felt anger, pity, hatred, indignation, pain, sadness.
"Sadness for George and for all black people who suffer from racism EVERY DAY!
"Whether in football, at work, at school, ANYWHERE! This has to stop, once and for all! Not tomorrow or the next day, it has to end TODAY!
"Violent acts of racism can no longer be tolerated. I can't tolerate. I won't tolerate. WE WON'T TOLERATE. Racism is ignorance. LOVE is intelligence."
On Sunday, Rashford's England teammate Jadon Sancho took off his shirt when celebrating scoring a goal for Germany's Borussia Dortmund, revealing a T-shirt with the slogan "Justice for George Floyd" written on the front.
Meanwhile, EPL leaders Liverpool's squad was pictured kneeling during training on Monday, with a caption "Unity is strength. #BlackLivesMatter".
Reds players Joe Gomez, Trent Alexander-Arnold, Jordan Henderson, Fabinho, Adrian, Virgil Van Dijk, James Milner and Dejan Lovren all tweeted the message.
England cricket also posted a photo of Jofra Archer, Adil Rashid and Jos Buttler embracing after last-year's World Cup victory, with the message "We stand for diversity, We stand against racism".
Top British sprinter Dina Asher-Smith added her voice to the protests: "Racism, police brutality..., all of this is something we all have to be vocal about. Irrespective of our race or nationality."
There have been several nights of unrest over race and policing in many US cities as a series of curfews failed to quell confrontations between some protesters and police.
Former England captain David Beckham posted on Instagram: "My heart goes out to George's family and I stand in solidarity with the black community and millions of others across the world who are outraged by these events. Its heartbreaking to see that in 2020 this is still happening."