GENEVA - Sir Peter Ustinov, a brilliant wit and mimic who won two Oscars for an acting career that ranged from the evil Nero in "Quo Vadis" to the quirky Agatha Christie detective Hercule Poirot, has died. He was 82.

Ustinov, a renaissance man whose talents included writing plays, movies and novels, as well as directing operas, also devoted himself to the world's children for more than 30 years as a goodwill ambassador for UNICEF.

He died of heart failure late Sunday night in a Genolier clinic near his home at Bursins in Swiss vineyards overlooking Lake Geneva, close friend Leon Davico, a former UNICEF spokesman, told The Associated Press.

"He was a great man. He was a human being. He was a unique person, someone you could really count on," said Davico.

Born in London on April 16, 1921, the only son of a Russian artist mother and a journalist father, Ustinov claimed also to have Swiss, Ethiopian, Italian and French blood - everything except English.

Ustinov delighted in national differences and frequently referred to them in his works and public appearances. He was - as he noted proudly in his autobiography "Dear Me" - conceived in St. Petersburg, Russia, baptized in a village near Stuttgart, Germany, and reared under a succession of Cameroonian, Irish and German nurses.

His imposing figure, variously described as resembling a teddy bear, a giant panda or a Georgian frontage, began 12 pounds at birth and stayed with him throughout his career.

Ustinov made some 90 movies and also had written books and plays. He directed films, plays and operas. His narration of Tchaikovsky's "Peter and the Wolf" won him a Grammy.

Among his film roles were a nomad in the outback who befriends a family in "The Sundowners," a one-eyed slave in "The Egyptian," Agatha Christie's Belgian detective Hercule Poirot in "Death on the Nile," and Abdi Aga, an illiterate tyrant with pretensions of learning in "Memed My Hawk."

Ustinov won best supporting actor Oscars for the role of Batiatus, owner of the gladiator school in "Spartacus" (1960), and as Arthur Simpson, an English small-time black marketeer in Turkey who gets caught up in a jewel heist in "Topkapi" (1965).

His Nero - the Roman emperor who presided over the throwing of Christians to the lions - won him a Golden Globe for best supporting actor in the 1951 movie "Quo Vadis."

He also won three television Emmys, portraying the English lexicographer Samuel Johnson in "Dr. Johnson" and as Socrates in "Barefoot in Athens." In "A Storm in Summer," his Emmy came for playing an aged Jewish delicatessen owner in Long Island at grips with racial prejudice in the shape of a proud black youth.

More recently he was the voice of Babar the Elephant, played the role of a doctor in the film Lorenzo's Oil, and in 1999 appeared as the Walrus to Pete Postlethwaite's Carpenter in a multimillion-dollar TV movie version of Alice in Wonderland.

Ustinov was married three times, and is survived by his four children and his third wife.

He had one daughter with his first wife, Isolde Denham, from whom he was divorced in 1950 after a decadelong marriage.

He married Suzanne Cloutier in 1954. They had two daughters and a son - noted sculptor Igor Ustinov. The couple divorced in 1971, the year they moved to Switzerland.

Ustinov married his third wife, Helene du Lau d'Allemans, in 1972.

No details on funeral arrangements were available.