Oscar-winning actor Philip Seymour Hoffman has died from an "apparent drug overdose" in his New York City apartment, an NYPD spokesman said.
The 46-year-old was found dead in his bathroom in the city's Greenwich Village area at 11.30am local time.
Awarded a best actor actor Oscar for his role in the 2005 film Capote, Seymour Hoffman checked into rehab in May for heroin use .
"He was found dead in his bathroom of an apparent drug overdose," an NYPD spokesman said.
Police were called by a friend of the actor, the spokesman said.
Speaking at the London Critics' Circle Film Awards in central London, John Hurt - who starred with Seymour Hoffman in 2003 film Owning Mahowny - said: "It's a devastating loss. His contribution was massive."
Celebrities paid tribute to the actor on Twitter.
Comedian Ricky Gervais wrote: " Such shocking & sad news. RIP Philip Seymour Hoffman. One of the greatest actors of a generation and a sweet, funny & humble man."
American singer and actress Lindsay Pearce posted: "Too many souls keep being lost to substance abuse. Thoughts to Philip Seymour Hoffman's loved ones and all affected by his loss. So sad."
Former England footballer Gary Lineker said: " Philip Seymour Hoffman's death is so sad. One of the World's greatest actors. Privileged to have seen him on Broadway. A terrible loss #RIP."
A spokesman for the British Academy of Film and Television Arts said: "We're shocked and deeply saddened to learn that Philip Seymour Hoffman has died."
Actress M ia Farrow wrote: "OH NO!!!!! Philip Seymour Hoffman has died. A truly kind, wonderful man and one of our greatest actors - ever."
She added: " Rest in peace Philip Seymour Hoffman. We who marveled at each of your performances, are grateful and very very sad."
Whoopi Goldberg wrote: " WTF!!!! philip seymour hoffman found dead in his apartment, a truly great actor... Gone.. I hope someone says hey whoop it's a hoax..
Steve Coogan said: " There are actors and there are movie stars and sometimes they're both but he was an actor first and a movie star second, although he was a movie star."
Speaking at the London Critics' Circle Film Awards, Coogan said: " He did some tremendous work. Everything he was in he raised the quality of his film just by his presence.
"People have different opinions about actors but you wouldn't find anybody who would have a bad word to say about any of his performances, they were all incredibly nuanced."
Skyfall actress Naomie Harris, who was also speaking at tonight's awards in central London, said: " That's a huge loss for everyone.
"He was an extraordinary and intelligent man, so it's incredibly sad, and it makes the evening all a bit more sombre now, having heard."
The news of Seymour Hoffman's death came after claims that his representatives had denied a death hoax spread earlier in the week.
The actor was currently working on the last instalment of the dystopian adventure franchise The Hunger Games, in which he played the role of head gamemaker Plutarch Heavensbee.
Born in Fairport, New York, in 1967, Seymour Hoffman got his first acting role in a 1991 episode of long-running police show Law and Order.
He went on to play memorable characters in films such as The Big Lebowski, Boogie Nights and Magnolia and also had a distinguished career in the theatre.
The actor leaves behind his long-standing partner and costume designer Mimi O'Donnell and their two daughters and son.
Seymour Hoffman had admitted to struggling with drug addiction in the past but had reportedly been clean for 23 years before a relapse last year.
"I went to rehab, I got sober when I was 22 years old," he said in a 2006 interview. "You get panicked... and I got panicked for my life."