Sony launches giant waterproof Xperia Z Ultra phone

Sony has announced a waterproof Android smartphone with a 6.4in screen (16.3cm).

The firm is pitching the Xperia Z Ultra as being the slimmest large-screened handset on the market, BBC reports.

It can also accept sketches or notes written using a standard pencil or metal-tipped pen in addition to an optional stylus.

The firm says it intends for the device to challenge Samsung's dominance of the jumbo-sized handset sector.

According to a study by consultants Transparency Market Research, Samsung accounted for 70% of the overall "superphone and phablet" market in 2012 thanks to the popularity of models including the Galaxy S3 and Galaxy Note 2.

Earlier this year, it added the Galaxy S4 and Galaxy Mega - a 6.3in-screened handset - to its line-up.

Sony already offers a 5in handset of its own, the original Xperia Z, which it unveiled in January.

The Ultra follow-up was unveiled at the Mobile Asia Expo in Shanghai. The new device will go on sale in China, Indonesia and Singapore in July and then in Europe in September.