"We take user privacy very seriously and are actively investigating this report," Apple spokeswoman Natalie Kerris told technology blog Recode.net on Monday, in response to reports that the photos were taken from the company's iCloud service.
Actress Mary Winstead addressed the photos via Twitter.
"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," she 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."
The FBI said it was investigating possible criminal violations in the breach of private files.
The images first appeared on an online bulletin board before spreading rapidly across the internet.
DPA