iTunes accounts linked to PayPal have been hacked with a number of users complaining that they have been cleaned out.
Apple and PayPal refused to discuss the details of the incident.
Experts have told the BBC there is no security hole in iTunes or Apple servers and that it is most likely users have fallen for an online scam.
"I just got hacked for $1,000 worth of software, videos and music," tweeted one victim.
Another told the technology blog TechCrunch: "My account was charged over $4,700. I called security at PayPal and was told a large number of iTunes stores accounts were compromised."
My iTunes account just got hacked and someone made about $700 worth of purchases. I contacted Paypal and they said Apple has gotten so many attacks since June, they can barely keep up with reporting them all."
Apple would not comment but said that they had recently implemented new security measures.
In a statement to BBC News, Apple said: "iTunes is always working to prevent fraud and enhance password security of all of our users.
BDST: 1955 HRS, 24 August 2010