Siri co-founder Dag Kittlaus leaves Apple

The man behind Siri, Apple's new voice-controlled personal assistant in the iPhone 4S, has left the US technology giant to pursue other projects.

Dag Kittlaus, the co-founder and chief executive of Siri, joined Apple as part of the company's acquisition of the voice control firm in April 2010.

The technology has since been incorporated as one of the headline features in the new iPhone 4S, which shifted more than 4m units after it went on sale earlier in the month.

All Things Digital reports that Dag has quit the company to be closer to his family and to brainstorm new entrepreneurial ideas. It is understood that he left just after the iPhone 4S launch.

After Norwegian-born Kittlaus founded Siri in 2007 along with Adam Cheyer and Tom Gruber, the company attracted significant investment until Apple swooped in to complete its acquisition.

As Siri was such an important part of the iPhone 4S launch, it is thought that Apple views voice control as a major growth area in the smartphone industry.

However, a flaw with the Siri system was discovered by security bloggers last week, involving the personal assistant allowing anyone to use the phone even when it is locked.