CANNES, France (AFP) -- Leonardo DiCaprio and Martin Scorsese were set for a victory lap at Cannes on Sunday after their Native American crime epic, "Killers of the Flower Moon" scored rave reviews, while the festival prepared to bow down before Jude Law as King Henry VIII.

Scorsese's latest opus, about a wave of murders among oil-rich Osage Indians in the 1920s, was showered in words like "searing," "triumph" and "masterpiece" by critics who scored the Cannes Film Festival's hottest ticket on Saturday night.

Based on a non-fiction bestseller, the film sees DiCaprio as a weak-willed man who marries a wealthy Osage woman and is drawn into the deadly schemes of his kingpin uncle, played by Scorsese's other long-time muse, Robert De Niro.

IndieWire said DiCaprio gives "his best-ever performance," while The Guardian awarded five stars for a "remarkable epic about the bloody birth of America."

The stars were due to address reporters later on Sunday.

But the festival was already set for another glitzy premiere later in the day, with "Firebrand" starring Jude Law as 16th-century English king Henry VIII alongside Alicia Vikander as his sixth and final wife, Catherine Parr.

While Scorsese's Apple-funded film had an out-of-competition slot at the festival, "Firebrand" is in the increasingly close race for its top prize Palme d'Or, to be announced on May 27.

Among the entries is Natalie Portman and Julianne Moore's new film "May December" which received positive reviews after its Saturday premiere.

The tale of a woman who caused a tabloid scandal by marrying a schoolboy -- and the actress who enters their lives years later to research a role -- was described as "deliciously campy" by IndieWire.

Portman told AFP she liked seeing women "behave in morally ambiguous ways."

"It always drives me crazy when people are like, oh, if only women rule the world, it would be a kinder place. No, women are humans and come in all different complexities," she said.

Arguably the current favourite for the Palme is British director Jonathan Glazer's "The Zone of Interest," a unique and horrifying look at the private life of a Nazi officer working at the Auschwitz concentration camp.

Critics were near-unanimous in their praise, Variety calling it "chilling and profound."

It was partly inspired by a book of the same name by British novelist Martin Amis, who died on Saturday at 73.

Also well received was "Four Daughters," a heartbreaking documentary about radicalisation within a Tunisian family that is both inventive and engaging.

That may go down well with jury president Ruben Ostlund, last year's winner for "Triangle of Sadness," who likes his arthouse films with some lighter touches.

A total of 21 films are in the main competition, with entries from past winners Wim Wenders, Ken Loach and Nanni Moretti still to come.

The weather has been untypically wet this year, but Cannes has had no shortage of splashy moments.

Law is not the only one playing a monarch -- the festival opened controversially with Johnny Depp's "comeback" film, "Jeanne du Barry," in which he takes the role of French king Louis XV.

Ageing Hollywood men have been a key theme of this 76th edition, with honorary Palmes for Michael Douglas and Harrison Ford, the latter at the world premiere of "Indiana Jones and the Dial of Destiny," as well as an appearance by Sean Penn for paramedics drama "Black Flies."