Apple has posted a new security warning for users of its iCloud online storage service amid reports of a concerted effort to steal passwords and other data from people who use the popular service in China.

The computer maker said in a post Tuesday on its support website that it was aware of organized attacks seeking to obtain user information. It said Apple's own servers have not been compromised but the company was taking the matter very seriously.

Apple's post did not mention China or provide any details on the attacks. But several news outlets reported Tuesday that some Chinese Internet users have begun seeing warnings that indicate they had been diverted to an unauthorized website when they attempted to sign into their iCloud accounts.