Five years after the release of the iPhone, there are now over a billion smartphone users worldwide, according to a report released Wednesday.

US research and consulting firm Strategy Analytics said the number of users topped one billion in the third quarter of 2012, with one out of every seven people worldwide carrying one of the devices.

The first smartphone, the Nokia Communicator, came out in 1996, but demand for the devices exploded after the release of Apple's iPhone in 2007.

"The iPhone revolutionized smartphone design and it catalyzed industry growth," Strategy Analytics Senior Analyst Scott Bicheno said in a statement.

"By the third quarter of 2011, we estimate there were 708 million smartphones in use worldwide. After a further year of soaring demand, the number of smartphones in use worldwide reached 1,038 billion units."

The research firm said it expected the number of users to double to two billion in less than three years.

"Smartphone penetration is still relatively low," Strategy Analytics Executive Director Neil Mawston said.

"Most of the world does not yet own a smartphone and there remains huge scope for future growth, particularly in emerging markets such as China, India and Africa."

Apple, which has sold more than five million of its latest iPhone 5 model since its release last month, nevertheless faces stiff competition from Samsung and other models powered by Google's Android software.