The Galaxy A8 is 5.9mm (0.23in) thick, making it less than 85% the thickness of Samsung's flagship Galaxy S6 Edge.

Despite this design constraint, engineers have still managed to fit in a relatively high capacity 3,050mAh battery and a 16-megapixel camera - albeit one that protrudes beyond the rest of the case.

One expert questioned the advantages of going so narrow.

For now, Samsung has announced only that the phone will go on sale in China and Singapore.

"The Galaxy A8 will not be coming to the UK," a spokeswoman told the BBC.

Although it will be the thinnest such device from one of the major manufacturers, other Chinese companies are already selling even more compact Android-powered rivals.

They include:

the Vivo X5 Max (4.75mm)

the Oppo R5 (4.85mm)

the Gionee Elife S5.1 (5.1mm)

China's overall smartphone market shrank for the first time in six years in the January-to-March quarter, coming in 4% smaller than for the same period the previous year, according to research company IDC.

But it said Samsung had experienced a much bigger fall than most - a 53% drop.

Trade-offs

One of the challenges of making a handset as thin as the Galaxy A8 is the need to minimise its risk of bending in the user's pocket.

Samsung has opted for a metal case to aid its rigidity, building on the engineering work it did for last year's original Galaxy Alpha.

The new machine also features:

a fingerprint sensor

a 4G chip

a 5.7in 1080p high-definition screen

But at 3,199 yuan (£330) it costs considerably more than Xiaomi's bestselling aluminium-framed similar-sized Mi Note, which is about 1mm thicker and 1,100 yuan (£115) cheaper.

"There's a perception that thin means quality, so perhaps that's one of the reasons that some companies are going so slim," said Ben Wood, from the telecoms consultancy CCS Insight.

"In China, in particular, smartphone-makers are fighting spec wars, so a feature like this can help their devices stand out.

"But I think we are reaching the limits - not just in terms of how tightly you can package the electronics and dissipate heat, but also in terms of battery technology.

"Users are tiring of devices that barely get through a day, and we may find that making a handset that's slightly thicker than the norm but with a much better battery life - that could emerge as a popular differentiator in future."

(BBC)