A rep for Jennifer Lawrence, who won an Academy Award in 2013 for her role in "Silver Linings Playbook," says photos of the actress posted online were stolen.

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NEW: An individual close to Ariana Grande says photos claiming to show her are "completely fake"

Online posts purport to show nude photographs of actress Jennifer Lawrence

Her publicist says it's a "flagrant violation of privacy" and authorities have been notified

Other celebrities also report they were hacked

CNN  — 

A publicist for Jennifer Lawrence slammed the appearance of nude photographs of the Oscar-winning actress online Sunday as a “flagrant violation of privacy.”

A hacker’s leak of nude photos of Jennifer Lawrence and other female celebrities is now a case for the FBI.

Posts on 4chan, Reddit, Twitter and Tumblr claim to include nude photographs of Lawrence, who won an Academy Award last year for her role in “Silver Linings Playbook.”

Celebrity blogger Perez Hilton posted what he said were naked photos of Lawrence and actress Victoria Justice, but he later took them down.

“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,” actress Mary Elizabeth Winstead wrote.

“Knowing those photos were deleted long ago, I can only imagine the creepy effort that went into this. Feeling for everyone who got hacked.”

Some celebrities said the photos were doctored.

Photos claiming to show Ariana Grande are “completely fake,” someone close to the singer said. Justice said pictures purporting to be of her are not real, either.

And actress Victoria Justice said pictures purporting to be her are fake.

Hacking of celebrity accounts has become more popular in recent years.

A judge sentenced Christopher Chaney of Florida to 10 years in federal prison in 2012 for stealing nude photos, scripts and personal information from the e-mail accounts of 50 entertainment industry figures, including movie stars Scarlett Johansson and Mila Kunis and singer Christina Aguilera.

The first real case of a celebrity hacking was in 2005. Hackers logged into Paris Hilton’s phone and stole photos of the reality star, said Mikko Hypponen, chief research officer at computer security company F-Secure, in 2011.

CNN’s Rachel Wells, Dave Alsup, Alan Duke and John D. Sutter contributed to this report.