Sony has officially announced a Wi-Fi-only version of its Xperia Z Ultra, morphing the smartphone into a mini-tablet.

It was only on Monday that we saw the Wi-Fi-only version leak through Sony's website, but the Japan-based company on Wednesday announced it's availability in its homeland.

In a press release, Sony refers to the new Xperia Z Ultra version as a tablet - which is pretty accurate given the 6.4-inch 1080p display could easily be judged as too big for a handset, but that didn't stop Sony from releasing it as such in October 2013.

Sony is sticking with the same specifications in the tablet version of the Xperia Z Ultra as the 3G version. You'll find a 6.44-inch display, Qualcomm Snapdragon 800 processor, 2GB of RAM, and a 3,050mAh battery which is fixed into the body rather than replaceable. It also packs GPS, Bluetooth 4.0, NFC and a waterproof build.

For customers who want a tablet smaller than 7-inches, the Xperia Z Ultra may be seen as a nice option, but it won't be cheap. The tablet goes on sale in Japan this week for roughly £300/$499 - a huge hike compared to the Nexus 7 or Kindle Fire line. Availability in the UK or US hasn't been announced, but we'll keep our eyes peeled for further information.