Tributes are being paid to US actor Chadwick Boseman, who played Black Panther in the celebrated superhero film set in a fictional African nation after he died on Friday aged 43.

"This is a crushing blow," wrote director Jordan Peele.

The Black Panther rallying cry "Wakanda Forever" trended online, as celebrities, civil rights activities and fans posted emotional messages.

The actor's cancer diagnosis was not publicly known.

"What a gentle gifted soul. Showing us all that greatness between surgeries and chemotherapy. This is what dignity looks like," wrote TV star and author Oprah Winfrey.

What a gentle gifted SOUL. Showing us all that Greatness in between surgeries and chemo. The courage, the strength, the Power it takes to do that. This is what Dignity looks like. https://t.co/U3OOnJVS42

— Oprah Winfrey (@Oprah) August 29, 2020

The eldest son of civil rights activist Martin Luther King said Mr Boseman "brought history to life" in his depictions of prominent black individuals including baseball player Jackie Robinson and soul singer James Brown.

May you have a beautiful return, King. We will miss you so. pic.twitter.com/jdip3RHoXb

— Ava DuVernay (@ava) August 29, 2020

Ava DuVernay, who has directed a string of powerful films and documentaries including Selma, about the fight for civil rights in the 1960s, wrote: "may you have a beautiful return, King."

May you have a beautiful return, King. We will miss you so. pic.twitter.com/jdip3RHoXb

— Ava DuVernay (@ava) August 29, 2020

Journalist Clint Smith echoed others on Twitter writing about how much Black Panther meant to his young son who idolised T'Challa, the character played by Mr Boseman.

Last year Mr Boseman said the film had changed what it meant to be "young, gifted and black".

He is "a big reason why our kids don't have to wonder about what a Black superhero is", tweeted writer Brian Josephs.

I keep thinking about my 3-year-old in his Black Panther costume. How he wore it almost every day when he got it, refused to take it off. The way he walked around saying “I’m the Black Panther.” How happy it made him. What Chadwick gave us was immeasurable. What an enormous loss.

— Clint Smith (@ClintSmithIII) August 29, 2020

Award-winning musician John Legend called Mr Boseman "a bright light [who] brought grace, elegance and power to everything he did. He always seemed to carry our ancestors with him".

I’m so shocked and heartbroken about Chadwick. He was such a bright light, such a gifted performer. He brought grace, elegance and power to everything he did. He always seemed to carry our ancestors with him. And now he joins them far too soon.

— John Legend (@johnlegend) August 29, 2020

Several on Twitter drew attention to the work that Mr Boseman produced while he was living with colon cancer after being diagnosed in 2016. "During that time, he gave us Civil War, Marshall, Black Panther, Infinity War, Endgame, 21 Bridges and Da 5 Bloods," wrote journalist Jemele Hill.

Hollywood has also paid tribute to the actor, including Marvel Studios which created Black Panther, as well as Disney and the Academy Awards which called it "an immeasurable loss".

Our hearts are broken and our thoughts are with Chadwick Boseman’s family. Your legacy will live on forever. Rest In Peace. pic.twitter.com/DyibBLoBxz

— Marvel Studios (@MarvelStudios) August 29, 2020

Fellow Marvel stars shared their feelings of loss on Twitter and Instagram. Mark Ruffalo, who plays the Hulk, wrote "All I have to say is the tragedies amassing this year have only been made more profound by the loss of Chadwick Boseman."

Tom Holland who is currently playing Spiderman said the actor was "even more of a hero off-screen" and called him a role model for millions around the world.