Christopher Nolan's biopic about the 'father of the atomic bomb' won best cast in a motion picture, while its star Cillian Murphy scooped the prize for best actor at the Hollywood ceremony.

Co-star Robert Downey Jr picked up the award for best supporting actor.

The red carpet event followed the longest actors' strike in history and is a key indicator for the Academy Awards, for which voting is currently taking place ahead of the 10 March ceremony.

Murphy, who has already enjoyed success at the BAFTAs and Golden Globes, said: "Twenty-eight years ago when I was trying to become an actor, I was a failed musician and I felt extremely like an interloper, but now looking out at you guys here today, I know I am part of something truly wonderful."

Accepting his award, Downey Jr said: "Why me, why now, why do things seem to be going my way?"

Picking up the prize on behalf of the cast, Sir Kenneth Branagh, who plays physicist Niels Bohr in the film, described the award as a "full circle moment" following the actors' strikes.

Paying tribute to the union, he said: "Thank you SAG-AFTRA, thank you for fighting for us.

"Thank you for every SAG-AFTRA member whose support and whose sacrifice allows us to be standing here, better than we were before."

He recalled the walkout of the Oppenheimer cast at last July's London premiere as the strike began.

He said: "We went from the red carpet and we didn't see the film that night. We happily went in the direction of solidarity with your good selves. So this is a full circle moment for us."

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Lily Gladstone was named best actress for her role as Mollie Burkhart in Martin Scorsese's Killers Of The Flower Moon, while Da'Vine Joy Randolph picked up the prize for best supporting actress for her role as Mary Lamb in The Holdovers.

"I am beyond humbled and I am so incredibly grateful to be considered among you," Randolph said of her fellow nominees Emily Blunt, Penelope Cruz, Jodie Foster and Danielle Brooks.

"How lucky are we that we get to do what we do... For every actor still waiting in the wings, it is not a question of if, but when. Keep going."

It was a successful night for TV comedy-drama The Bear, the story of a star chef who returns to Chicago to run the family business after the death of his brother.

Stars Jeremy Allen White and Ayo Edebiri were presented with the awards for best actor and actress in a comedy series respectively, while the series won best ensemble in a comedy series.

Steven Yeun and Ali Wong won best actor and actress in a limited series for their roles in Beef, about a pair who start a life-changing feud after a road rage incident.

Actor Pedro Pascal appeared visibly shocked and emotional as he appeared on stage to collect the award for best male actor in a drama series for his role in The Last Of Us.

"This is wrong for a number of reasons, I'm a little drunk, I thought I could get drunk. I'm making a fool of myself, but thank you so much for this," Pascal told the audience.

He later told British star Tan France he was going to celebrate the win by kissing Succession star Kieran Culkin as "revenge", as the pair have made jokes at each other's expense during their awards season speeches.

Sky Atlantic TV hit Succession, about warring siblings in a media dynasty, was named best ensemble for a drama series.

Star Alan Ruck said the cast had made "friends for life" and described it as "one last hurrah" following the end of the last series.

"Right now, you are looking at some of the luckiest people on the planet. And some of the most grateful," he said.

"Because not only did we get to work on one of the best television shows maybe ever, we made friends for life.

"I think the magic of Succession was the writing was so fabulous it inspired all of us to bring our A game from the very beginning, we got off watching each other work, we caught lightning in a bottle. Lucky."

Hollywood star and singer Barbra Streisand was honoured with the SAG Life Achievement Award.

Meryl Streep, Anne Hathaway and Emily Blunt who starred in the 2006 hit film The Devil Wears Prada reunited on stage to present the award for best male actor in a comedy series.

British star Naomi Watts introduced the in memoriam segment of the show, which honoured actors including Harry Potter star Sir Michael Gambon and Friends actor Matthew Perry.

The ceremony was streamed on Netflix for the first time, and is one of the service's most significant forays into live streaming so far - with a live tennis event to follow next month.