Robert Downey Jr and Da’Vine Joy Randolph have taken out the best supporting actor awards at this year’s 96th Academy Awards.

Downey Junior won an Oscar for his role playing Lewis Strauss, the former chairman of the US Atomic Energy Commission in Oppenheimer.

Strauss’s efforts were later exposed during a congressional hearing, as he sought confirmation to serve as President Dwight Eisenhower’s commerce secretary.

Critics praised Downey for playing against his conventional type. He was considered a frontrunner, having collected Golden Globe and Screen Actors Guild trophies for his co-staring role.

The US actor earned his first Oscar nomination for playing Charlie Chaplin in 1992’s Chaplin. After battles with scandal and addiction, he earned a second supporting-actor nomination for his role in the war satire Tropic Thunder.

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Earlier, Randolph won the best supporting actress Oscar for her role as the grieving mother Mary Lamb in the boarding school drama The Holdovers.

While it’s the first Oscar for the Black American actress, Randolph has dominated with a Golden Globe, a Critics Choice Award, a BAFTA and a SAG award for her role as the cafeteria manager at the New England school.

The drama sees three people thrown together at Barton Academy during the Christmas holidays in 1970.

Mary Lamb, who is mourning the death of her son in Vietnam, is joined by a cranky teacher played by Paul Giamatti and a troublemaking student, played by Dominic Sessa.

The 37-year-old Yale School of Drama alumni, who got her start in theatre, has said she is grateful to hear from audiences who resonate with Mary’s sense of loss and apathy toward the holidays.

“Imagine how hard it is if you’re going through something and all that is on your TV is cheery, cheery, cheery, and you don’t feel like that on the inside,” Randolph told Reuters.

Meanwhile, Britain’s The Zone of Interest, about a German officer’s family living next door to the Auschwitz extermination camp during World War II, collected the Oscar for best international feature film.

Prior to the awards, hundreds of pro-Palestinian protesters angered by the Israel-Gaza conflict shouted and slowed traffic in the blocks surrounding the Dolby Theatre in Hollywood. “While you’re watching, bombs are dropping,” one sign read.

“The Oscars are happening down the road while people are being murdered, killed, bombed,” said 38-year-old business owner Zinab Nassrou.

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Oppenheimer, the three-hour drama directed by Christopher Nolan, led the field with 13 nominations. The movie is the frontrunner to win the prestigious best picture prize, capping its sweep of other major awards this year.

After 2023 was marred by actors and writers strikes, the Oscars give Hollywood a chance to celebrate two global hits.

Oppenheimer and feminist doll adventure Barbie, another best picture nominee, brought in a combined $US2.4 billion ($3.6 billion) in a summer box office battle dubbed “Barbenheimer”.

-with AAP