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Sony has unveiled what it says is the thinnest tablet computer of its kind.

The Android-powered Xperia Z is 0.27in (6.9mm)-thick. That is 0.01in thinner than Apple's iPad Mini despite featuring a bigger 10.1in screen.

It coincides with news that LG is releasing a 5in handset - the Optimus G Pro - making it the latest to offer the so-called "phablet" form factor.

Both devices have only been confirmed for release in Japan, but more details are expected next month.

Mobile World Congress is being held in Barcelona from 25 to 28 February and is a popular time to announce global launches of new smart devices.

Samsung has already said it would show off a new 8in version of its Galaxy Note tablet family at the event.

Beyond being thin, Sony's new tablet can also lay claim to being the lightest for its size.

The - a fraction below the Toshiba Excite 10 LE which previously laid claim to the title.

In addition it is water and dust-resistant - featuring similar plastic covers to protect its ports as are found on the firm's Xperia Z smartphone which was announced a fortnight ago at the Consumer Electronics Show (CES) in Las Vegas.

The two Sony devices are designed to work together, allowing photos and other data to be transferred between the phone and tablet using the firm's "one-touch sharing" facility which is activated by waving the machines close to each other to activate their near field communications (NFC) chips.

"It's a good product and on the face of it it should do well, but it is hampered by a potential squeeze on the larger tablet segment as a lot of consumers and other manufacturers are moving to the smaller 7in-to-8in form factor - in part because of their cheaper price," David McQueen, principal analyst at the Informa Telecoms and Media consultancy, told the ´óÏó´«Ã½.

"So the success of the Sony tablet might ultimately be determined by how much it costs as well as whether the firm bundles some of the content it owns from its music, movie and gaming divisions."

is effectively a version of its existing Optimus G phone with a bigger, more detailed screen.

It offers 440 pixels per inch (ppi) - matching HTC's newly-released J Butterfly and Huawei's Ascend D2.

This density of its pixels allows LG's handset to be marketed as offering playback of 1080p videos in their full high definition resolution.

However, the trade-off is the screen is power-hungry. LG's handset features a 3,000 mAh (milliampere-hour) battery as a consequence which is bigger than that of most other smartphones.

"4G high-speed data connections are helping push the adoption of higher definition bigger screens on phones," said Mr McQueen, "but I do think it will remain a small, though high-end, segment of the market."

Sony and LG's devices were revealed as part of Japanese network NTT Docomo's Spring line-up announcement.

It also featured a more unusual handset from NEC Casio featuring two screens.

The are placed on either side of the device, but can also be folded out so that the two 4.3in LCD screens sit alongside each other.

It is the second dual-screened smartphone to be announced in recent weeks - Russia's Yota unveiled a model in December which features one LCD screen and one e-ink display, which it said would go on sale in the second half of the year.

However, recent history suggests such devices might only appeal to a niche audience.

Samsung, LG and Kyocera are among others firms to have released dual-screened phones over the past two years which only achieved limited sales.