Sony Corp Logo
A logo of Sony Corp is pictured at an electronic store in Tokyo May 14, 2014. Reuters/Toru Hanai

Sony Xperia Z5, Xperia Z5 Compact and Xperia Z5 Premium owners in Japan can now update their smartphones to Android 6.0 Marshmallow, pushing the rumour mill into overdrive with expectations that the software upgrade will soon be made available for Z5, Z5 Compact and Z5 Premium users outside Japan.

Speculations also indicate that the latest Android build will soon be made available to the Xperia Z4, Xperia Z3+, Xperia Z3, and Xperia Z2 models.

DoCoMo, a carrier from Japan, recently released the Android 6.0 update for the entire Xperia Z5 lineup. Sony Japan has also released a slew of snapshots for the Android 6.0 Marshmallow update, Phone Arena reported.

In February, a Sony Mobile representatives had tweeted that beginning from March 7, owners of Xperia Z4 Tablet, Xperia Z4+, Xperia Z5, Xperia Z5 Compact, Xperia Z5 Premium in the UK wouldd be eligible for the update. Xperia Blog has also reported that the Android 6.0 Marshmallow update with build number 32.1.A.0.434 has been certified for Xperia Z3+.

In the last quarter of 2015, Sony had started an Android 6.0 beta testing program for owners of the Sony Xperia Z3 and Xperia Z3 Compact. The beta program made it possible for registered users to run the Android 6.0 on their devices and send feedback to the Japanese tech giant.

Since the beta program was appreciated by Z3 and Z3 Compact owners, the Xperia Z2 is now also included in the program. Moreover, the Xperia beta program is available for more countries: Denmark, Estonia, Finland, Germany, Iceland, Ireland, Italy, Latvia, Lithuania, Netherlands, Norway, Spain, Sweden and the UK.

Most of Sony's Xperia Z series devices are currently running on the Lollipop version of Android. Rumours suggest incremental updates like Android 5.1.1 will be skipped and the devices will be directly upgraded to Android 6.0. Apart from the Xperia Z models mentioned above, the Android 6.0 upgrade will also arrive for the Xperia Z3 Tablet Compact, Xperia Z2 Tablet, Xperia M series like M5 and M4 Aqua, Xperia C series C5 Ultra and C4.