LONDON, Oct 4 (Reuters) - Vodafone Group Plc <VOD.L>, Europe's largest mobile phone company, will start selling multimedia phones for its Live! service on October 14, a salesman at one of Vodafone's stores said on Friday.

The launch means Vodafone will join rivals Orange <ORA.PA>, T-Mobile <DTEGn.DE> and mmO2 <OOM.L> in offering a multimedia messaging service (MMS) in Britain, which includes the picture messaging that Vodafone Chief Executive Christopher Gent has identified as an important source of new revenue.

"There's going to be a big announcement on the 14th and then we'll start selling them," the salesman at a central London shop said.

A spokeswoman at Vodafone declined to comment on the timing of the launch.

When Vodafone reported its full-year results in May, Gent said picture messaging would be a "killer application" that would attract new customers and lead existing subscribers to upgrade their phones.

Vodafone Live! will run on the general packet radio service (GPRS) technology, which operators hope will whet consumer appetites for third-generation mobile services that allow video clips and music to be delivered to phones at high speeds.

MmO2 <OOM.L> said on Tuesday it would launch its MMS service later in October.