Mobile phone operator Softbank on Tuesday unveiled a smartphone that can measure radiation as consumers in Japan clamour for reassurance following last year's Fukushima nuclear disaster.

The latest model in the firm's Pantone series comes complete with a sensor that enables users to see at the touch of a button how much radiation they are being exposed to.

The phone, which the company is putting on general sale from July, can also keep a record of exposure in every location the phone has been to, Softbank said in a statement, adding that it can detect gamma rays in a range of 0.05-9.99 microsieverts per hour.

Japan's top operator NTT DoCoMo at a tech fair last year showcased a smartphone with a changeable "jacket" that measures radiation levels. DoCoMo at that time said they were undecided on the product's commercial launch.

Many people in Japan remain concerned about radiation since the 9.0-magnitude quake and tsunami of March 2011 sparked the world's worst nuclear crisis in a generation at the Fukushima atomic plant.

Worries over the health implications of the radioactive leak have sent demand for radiation-measuring devices soaring in Japan.