"This decision was made for the health of the family. She will not be commenting, and asks that the family be given its privacy at this time," lawyer Robert Offer said in a statement.

The Oscar-winning actress filed in Los Angeles Superior Court on Monday, citing irreconcilable differences, court documents showed.

Jolie sought full physical custody of their six children aged eight to 15 with visitation rights for Pitt but did not seek spousal support.

Jolie cited their separation date as September 15.

"I am very saddened by this but what matters most now is the wellbeing of our kids," Pitt said in a statement to People magazine.

"I kindly ask the press to give them the space they deserve during this challenging time."

Jolie and Pitt, known collectively as "Brangelina", were one of the entertainment world's most visible couples, due to their good looks, successful films and activism. They married in August 2014 after 10 years together.

Their relationship was steady fodder for tabloids with reports focusing on what role Jolie played in the break-up of Pitt's marriage to actress Jennifer Aniston, and, more recently, possible trouble in the marriage.

News of their split set social media buzzing, and #brangelina quickly emerged as the top trending topic on Twitter.

Jolie, 41, who won a best-supporting actress Oscar for Girl, Interrupted in 2000, was previously married to actors Jonny Lee Miller and Billy Bob Thornton.

Pitt, 52, was married to Aniston in 2003 when he and Jolie began filming Mr & Mrs Smith, the story of assassins unknowingly assigned to kill each other.

There were reports of an affair, but Jolie told Vogue magazine they were only "very, very good friends" until Pitt and Aniston split in 2005.

Before their wedding at their French estate, Jolie and Pitt had said they would not wed until same-sex couples were allowed to marry.

While Pitt and Jolie won praise for their on-screen chemistry in Mr & Mrs Smith, their most recent film collaboration, By the Sea, last year was about a married couple drifting apart. Jolie wrote and directed the film.

Jolie has been estranged from her father, actor Jon Voight, but he told Inside Edition he was concerned about the divorce filing.

"It's very sad," he said. "Something very serious must have happened for Angelina to make a decision like this."

Peter Walzer, a California lawyer who represented actress Katie Holmes in her divorce from actor Tom Cruise, said in a phone interview it was unusual that Jolie had sought sole physical custody, and it was tantamount to saying Pitt was not competent to be a parent.

"It's an insult," Walzer said.

Hollywood entertainment website TMZ, citing a legal filing, said Jolie "was extremely upset" by Pitt's parenting methods.

Media commentators reacted to the news with surprise and sadness.

"Today shall go down as the day love died," Vogue said in an online report on the couple's split.

Jolie had an offbeat reputation early in her career but has taken on humanitarian causes and was named a special envoy for the UN High Commissioner for Refugees.

She travelled to Afghanistan, Sudan, Tanzania, Iraq and Jordan to call attention to the plight of refugees and the underprivileged.

Pitt joined Jolie on some of her trips and started a foundation to finance reconstruction of homes in New Orleans after Hurricane Katrina. Together they started the Jolie-Pitt Foundation in 2006 to help charities worldwide.

Their children include sons adopted from Cambodia and Vietnam and a daughter adopted from Ethiopia, as well as three biological children.

To encourage other women, Jolie spoke out publicly about elective surgeries in 2013 and 2015 to remove her breasts, ovaries and fallopian tubes as a preventive measure due to a family history of cancer.

In addition to her Oscar win, Jolie was nominated for an Academy Award for Changeling in 2008.

Pitt's breakout role came in a supporting part in Thelma & Louise in 1991. His other films include The Curious Case of Benjamin Button, Inglourious Basterds, Moneyball, and the Ocean's 11 films.

Reuters