Oscar-winning French actor Marion Cotillard has swiftly shut down rumours that she and her Allied co-star Brad Pitt - the soon-to-be third ex-husband of Angelina Jolie - are having an affair.

When news broke Jolie had filed for divorce, the online peanut gallery and tabloids went searching for reasons.

One of the conclusions drawn was that Pitt had fallen for his leading lady - just like he did in 2004 on set of his and Jolie's first film together, Mr. & Mrs. Smith.

Cotillard, 40, was not taking the unsubstantiated claims she is this month's "Becky with the good hair" lying down and turned to Instagram to quash speculation about her personal life with a lengthy statement and an image invoking terror that hasn't been seen since Alfred Hitchcock's The Birds.

"This is going to be my first and only reaction to the whirlwind news that broke 24 hours ago and that I was swept up into," she said.

"I am not used to commenting on things like this nor taking them seriously but as this situation is spiraling and affecting people I love, I have to speak up."

Then, killing two birds with one stone, she turned the subject to her partner, French actor and director Guillaume Canet, and officially confirmed that she is pregnant with her second child.

"Many years ago, I met the man of my life, father of our son and of the baby we are expecting. He is my love, my best friend, the only one that I need."

The pair, who met in the 1990s, starred in the 2003 film Love Me If You Dare when Canet was still married to actor Diane Kruger. Their first child, Marcel, was born in 2011.

The La Vie en Rose star is not accustomed to appearing in gossip magazines, she is usually featured in high-end publications who run the Dior campaigns she regularly fronts or on best dressed lists.

She has no time for this "crafted conversation" and ended her statement, which was written in both English and French, to send her best wishes to everyone involved in Branglexit.

"To those who have indicated that I am devastated, I am very well thank you. This crafted conversation isn't distressing. And to all the media and the haters who are quick to pass judgment, I sincerely wish you a swift recovery. Finally, I do very much wish that Angelina and Brad, both whom I deeply respect, will find peace in this very tumultuous moment. With all my love Marion."

Jolie and Pitt separated on September 15 before she filed for divorce on Wednesday citing "irreconcilable differences".

"This decision was made for the health of the family," Jolie's lawyer Robert Offer said.

Pitt released a statement soon after, saying: "I am very saddened by this, but what matters most now is the well-being of our kids."

The couple have six young children aged between eight and 15. Jolie, 41, has requested sole physical custody with Pitt, 52, allowed visitation rights. She is not requesting spousal support. They have a $500-million fortune and 12 years of combined assets, mainly in real estate.

A number of reports suggest Pitt is "upset" and plans to attempt to fight accusations of his alleged alcohol consumption, marijuana smoking, anger issues and bad parenting methods as cited by TMZ.