The document describes a flexible touchscreen display which would communicate with a smartphone or other electronic device.

It coincides with a report from a tech consultancy suggesting there is huge pent up demand for such a gadget.

But ABI Research warns that battery life issues still need to be addressed.

It says assuming such problems can be resolved, about 485 million wearable computing devices might ship by 2018, providing a significant growth opportunity for Apple and the wider consumer electronics industry.

Not all published patents lead to actual products, but Bloomberg, the Wall Street Journal and the New York Times have all published reports this month saying sources had confirmed Apple was experimenting with a watch-like device.

The iPhone-maker declined to comment when contacted by the BBC.

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 (BBC News Technology)