The 35-year-old who was in Paris for Fashion Week is believed to have pleaded with the attackers for her life, saying it was the "worst moment of my life" and that she was a mother of two young children, according to TMZ.

"She begged for them to let her live and (said) she has babies at home... She thought they were for sure going to kill her," the unidentified source told E! News.

She was not physically harmed but was left "badly shaken", a source said.

The source said the attackers fled on bicycles.

As investigations continue in Paris, Kardashian West was reunited on Monday with her rapper husband, Kanye West, after she touched down in New York on a private jet.

Kardashian West, wearing sunglasses and with her head bowed, was pictured entering her Manhattan apartment with her husband. She was clearly not wearing her engagement ring, prompting fears it might have been stolen in the robbery.

She had left Paris by private jet hours after the robbery. Kardashian West, who her publicist said was "badly shaken but physically unharmed," said nothing to waiting media upon her arrival.

Accompanying her was her main bodyguard Pascal Duvier who has come under criticism for not stopping the robbery. According to reports he was with Kardashian West's two sisters Kourtney Kardashian and Kendall Jenner at a nightclub when the attack occurred.

An official told Us Weekly magazine the ordeal began at about 2.25am when the gang of five entered the star's luxury apartment, purchased by Kanye West.

A male concierge was handcuffed, tied up, gagged and hidden in a cupboard in the stairwell of the building. The men then made their way up to the apartment where Kardashian West had just finished a FaceTime call with her brother Rob Kardashian.

iTELE television said the star was bound with packing tape and had a gun pointed at her temple. She was locked in the bathroom.

About US$10 million ($13 million) worth of jewellery was stolen, police confirmed.

The reality star, who has been attending Paris Fashion Week with her mother Kris Jenner and sisters Kourtney and Kendall, was not physically harmed during the terrifying incident but was said to be "badly shaken".

Her engagement ring alone - a 15 carat square-shaped solitaire diamond set on a thin pave band - is worth more than $1.25 million. It is not yet known whether that has been stolen.

The men, who are still at large, fled on bikes.

Kardashian West left Paris on a private jet at 9.30am.

She had been in Paris to attend fashion shows and was being dressed by numerous luxury labels for various events being held all around the city. A film crew for her reality series, Keeping Up With The Kardashians was also in tow.

Her social media accounts have been flooded with images and footage of gifts arriving at her accommodation, including a rare mink jacket by Riccardo Tisci for Givenchy, python skin pants and boots by Alaia and Balmain looks taken straight from the runway.

The attack happened in a discreet luxury residence behind the city's Madeleine church, which has several secret entrances, and is preferred by film and music stars.

Kardashian West has stayed there at least once before, in 2014, before her marriage to rapper Kanye West.

Images of Kris' partner, Corey Gamble, eating breakfast in the nearby restaurant of the Four Seasons Hotel George V, were circulated on Instagram just days ago. Basic rooms in the exclusive hotel - where security is reportedly tight - start at about $1700 per night.

Just three-hours prior to the robbery, the reality star was posting videos to Snapchat from her room after retiring for the night following the Balenciaga show, a private dinner hosted by the label Alaia and the Givenchy show.

When her husband Kanye West was told of the attack he abruptly ended a performance in New York less than an hour into his set on Sunday night.

"I'm sorry I have a family emergency, I have to stop the show," West told the audience in video tweeted by fans.

Celebrities, some who are not fans of the attention loving family, have come out in defence of the 35-year-old.

The Late Late Show host James Corden, who regularly uses the Kardashian and Jenner clan as punchlines, called for Twitter to stop making jokes at her expense.

"People making jokes about Kim Kardashian tonight would do well to remember that she's a mother, a daughter, a wife, a friend. Be nice or shut up," he tweeted.

Family friend, model Chrissy Teigen, also sparked debate about the cult of celebrity after the incident.

"Some shit just isn't funny. I see you trying, but it isn't," she wrote. "Fame is interesting. Celebs are supposed to love you guys while also knowing you'd make a meme of our dead bodies to get retweets."

This latest security scare - despite her having a number of full time bodyguards - follows last week's incident with serial pest Vitalii Sediuk who tried to assault her on the street in Paris.

She was on her way for dinner at celebrity haunt Restaurant l'Avenue when Sediuk launched himself at her in an attempt to kiss her behind.

Sediuk was intercepted by Kardashian West's long-time bodyguard, Pascal Duvier, who swooped in before Sediuk made contact with the star and knocked the self-described "entertainment Hollywood reporter" to the ground.