The FBI is investigating after nude photos of Oscar-winning actress Jennifer Lawrence and other female stars were stolen and posted online.
The intimate images first appeared on an online bulletin board in the US before going viral.
More than 60 photographs of Lawrence were among those reportedly stolen after what some have said could have been an iCloud leak which allowed celebrities' phones to be hacked.
A representative for the US actress confirmed the images are genuine.
"This is a flagrant violation of privacy. The authorities have been contacted and will prosecute anyone who posts the stolen photos of Jennifer Lawrence," a statement said.
A list of those who have allegedly been hacked has also appeared on the web, Buzzfeed reported.It contains more than 100 names, including Aubrey Plaza, Cat Deeley, Kelly Brook, Kim Kardashian, Michelle Keegan, and Rihanna. The hacker also claims to have a "full set" of photographs of US soccer star Hope Solo.
Actress Mary Elizabeth Winstead, who was on the list, tweeted: "To those of you looking at photos I took with my husband years ago in the privacy of our home, hope you feel great about yourselves."
In another post she said: "Knowing those photos were deleted long ago, I can only imagine the creepy effort that went into this. Feeling for everyone who got hacked."
But a spokesman for the singer Ariana Grande said photographs that claimed to show her are fake.
And the actress Victoria Justice also denied images purporting to show her are real.
She tweeted: "These so called nudes of me are FAKE people."
A representative from Apple told Sky News they are not currently commenting on allegations it was an iCloud leak.
The FBI has investigated previous leaks of nude celebrity images, including those of Scarlett Johansson and Christina Aguilera.