A group of independent programmers has claimed that it had "unlocked" the latest generation of Apple Inc iPhones so the devices can be used on unauthorized wireless networks, in a move that could threaten the company's carrier partners.

Since the original iPhone was launched in June 2007, Apple has struck partnerships with wireless carriers worldwide, such as in US with AT and T Inc and France Telecom SA's Orange unit, media reports said.

Under these agreements, the iPhone can generally be used only by subscribers to those carriers but now as a group, called the iPhone Dev Team, has released a free piece of software called "yellowsn0w" that unlocks the iPhone 3G, the phones could be used via non-authorized networks also, the Wall Street Journal reported.

Yellowsn0w, is the software which lets users reprogramme the phones so they can work on any wireless network  based on the same technical standard.

However, several users were also quoted as saying that they successfully installed the software on their iPhone 3Gs and were able to make calls on non-authorized networks.

An Apple spokeswoman, the paper said, declined to comment on the iPhone Dev Team's work, only saying that Apple doesn't support unlocked iPhones in the US.

Apple offers such phones in Germany and Hong Kong "where government regulation requires it" but they usually  come at a steep price, the paper said.