A spokesperson for Kardashian said she was “badly shaken but physically unharmed” after the assault, which occurred late on Sunday.
Paris police said the items stolen were worth “several million euros” and were “mostly jewellery”.
The spokesperson said “two armed masked men dressed as police officers” had entered Kardashian’s residence in a chic district of Paris and held her up at gunpoint.
On hearing the news, Kardashian’s husband, rap superstar Kanye West, abruptly ended an appearance at a festival in New York, citing a “family emergency”.
Kardashian, one of the most recognisable US celebrities, had made a series of high-profile appearances at Paris fashion week.
The 35-year-old had attended catwalk shows by Balenciaga and Givenchy on Sunday and had also appeared at a launch for Armenian-American jewellery designer Siran Manoukian.
The Los Angeles-born designer and socialite, a longtime friend of Kardashian, was launching her own clothing label Maison Siran.
A spokeswoman for Maison Siran told AFP that their jewellery was “extremely premium”, but could not confirm that Kardashian had been loaned any of it, as is often the case for fashion shows and film premieres.
On Monday, a gaggle of journalists and fans gathered outside the red painted door of the luxury residence where Kardashian had been staying in the Madeleine district of Paris near the city’s main department stores.
A waiter at a cafe opposite said: “Only stars stay there. Kanye West, Jay Z. Kim Kardashian has been there for a week, I have seen her coming and going.”
Kardashian was last week approached in Paris by Vitalii Sediuk, who carries out pranks on stars. He was caught on video attempting to kiss her behind in an apparent social commentary.
Kardashian, who has two children with West, has been a fixture of US celebrity news for more than a decade after the leak of a sex tape and on the back of reality show “Keeping Up with the Kardashians”.
– Swift exit for Kanye –
West learned about the assault as he headlined a music festival in New York.
One of the biggest draws in live music, West took to the stage half an hour late but in dramatic fashion with a fireworks show overhead as he ripped into songs from his latest album “The Life of Pablo.”
However, an hour into his set, West said mid-song, “I’m sorry, show’s over,” and quickly left the stage.
A festival representative took the microphone to declare a 10-minute intermission before quickly returning to say that West had a “family emergency” and had already left the venue.
The festival later issued a statement praising West for a “great show” and said: “Our thoughts are with West and his family.”
West had flown to Paris to appear with his wife and her sister Kourtney Kardashian on Thursday during a one-day break in his North American tour.
Amid an initial lack of details over his swift exit, many fans at the festival were distraught as they poured out of the venue into the parking lot of the New York Mets’ baseball stadium.