PARIS • It seems hard to believe, but Monica Bellucci - who has spent four decades in the limelight as a model and actress - suffers from stage fright.

Now appearing on stage in Paris, incarnating opera singer Maria Callas, the Italian diva confesses experiencing pure "terror".

"It is not that I was afraid of theatre, I am still afraid of theatre. I tremble," the 55-year-old said. "Going on stage is almost a kind of violence I put myself through."

Bellucci is playing the 20th-century opera star in a month-long show titled Maria Callas: Lettres Et Memoirs (Maria Callas: Letters And Memories) at the Bouffes Parisiens theatre until March 28.

Film acting, said the actress, who has played in two The Matrix movies (2003) and was a Bond girl in the 2015 movie Spectre, is less intimidating.

"When one makes a film, it is as if one is protected from the outside world," Bellucci said. "With theatre, one breathes in the public and the public breathes you in. There is a direct contact."

With theatre, she added, one's concentration must last for the duration of the show. With film, scenes are shot one by one, with rests in between.

Only once, in director Gaspar Noe's film Irreversible (2002), has she shot a scene that lasted as long as 20 minutes, she said.

In spite of her fear, Bellucci was captivated by director Tom Volf's project on Callas, known for her tragic love affair with Greek billionaire Aristotle Onassis almost as much as for her captivating voice.

The biographical show draws heavily on letters and writings by Callas, collected by Volf, who has also made a movie titled Maria By Callas (2017).

"The letters are so beautiful... it was impossible not to see into the soul of this wonderful artist," said Bellucci.

For Volf, a sort of "chemistry" occurred between Bellucci and Callas on stage.

The actress, he said, "interpreted with accuracy the strength and vulnerability of the diva. With her celebrity status, Monica was able to understand the woman behind the legend".

Bellucci even wears one of Callas' dresses in the play.

"What is incredible is that there was no need to make a single adjustment - it was as if it was made to measure," said Volf.

The glare of the spotlight is another thing the two women shared.

Callas lived with details of her personal life splashed on the world's front pages - from her legendary success to her alleged capriciousness to the heart-breaking affair with Mr Onassis, who ended up marrying Mrs Jackie Kennedy, widow of assassinated United States President John F. Kennedy.

"She showed this smiling public image, and behind it was hidden a woman experiencing something quite different," said Bellucci.

"When one is exposed, one is at great risk. Me, I try to protect myself... It is truly important to keep your feet on the ground and to keep a distance from your (public) image," said the actress, whose separation from actor Vincent Cassel after a 17-year relationship also received wide press coverage.

Does she mind being described as a diva, as was Callas before her?

"One of my daughters is named Deva. It is not a negative thing. In Italian, it means someone who takes the light from the sky," she said.

AGENCE FRANCE-PRESSE