A hacking group on Wednesday said it has obtained a million identification numbers for Apple mobile devices after breaking into the laptop of an FBI agent, a claim which the federal probe agency said has "no evidence".

Anonymous affiliate - AntiSec - released a file on the internet which allegedly contained a million identification numbers for the Apple devices.

The group said they obtained the data by hacking into the computer of an FBI agent in March.

Responding to the claim, the federal agency said it is aware of reports alleging that an FBI laptop was compromised and private data regarding Apple unique device identifiers (UDIDs) was exposed.

UDIDs are 40-character strings of letters and numbers assigned to Apple devices.

"At this time, there is no evidence indicating that an FBI laptop was compromised or that the FBI either sought or obtained this data," the FBI said in a statement.

AntiSec had posted copies of the file over the weekend and claimed it has a total of 12 million numbers for iPhone, iPad and iPod Touch devices, as well as some phone numbers and personal data on their owners.

The group said the purpose of their hacking into the FBI agent's laptop and releasing the data was to prove that the agency used device information to track people.

AntiSec said they had obtained the file from the computer of Christopher Stangl, a supervisory agent of the FBI's Cyber Action Team.