Chinese computer maker Lenovo presented a new tablet device including a hinge-cum-handle allowing it to tilt and stand, a feature it billed as a "game-changing" innovation.

Hollywood actor Ashton Kutcher unveiled the Yoga Tablet at a Los Angeles event which had been shrouded in mystery, with teaser videos and social media hints tagged #betterway.

The device, which has 18 hours on a single battery charge and goes on sale Wednesday, has three modes: hold, tilt and stand. A cylindrical hinge on one side can either be held, or opened to produce a stand, similar to the kick-stand on Microsoft's Surface tablet.

"Watching and discovering that people frequently use tablets in three main ways allowed us to break the mold on the current 'sea of sameness' designs," said Lenovo senior vice president Liu Jun, calling it "game-changing."

Teaser videos ahead of the event had included some suggesting that it could somehow be attached to furniture or household appliances. But the product appeared less radical.

"For this me is a risk," Kutcher said in a livestreamed event from Los Angeles, praising Lenovo for realising that "the risk is to be taken now because this is happening in the world now.

"They understand that they have to take risks and lead," added the "Two and a Half Men" actor, who is known as a tech investor, and who donned a "Lenovo product engineer" badge for the presentation.

The device comes in 8 and 10 inch models, priced at $249 and $299 respectively. An optional bluetooth keyboard is available for the larger model, which serves as a cover.

It enters a hugely crowded tablet market still dominated by Apples iPad, but with rivals including notably South Korea's Samsung vying to attract customers in the run-up the all important US holiday gift-buying season.

The design looks like a wireless Apple keyboard, and observers noted that the extra space in the hinge/handle allows Lenovo to boost the battery charge to last longer than that of many competing tablets.

The devices run on Google's Android operating system, and have relatively low-resolution 1280 x 800 screens.

Tech website the Verge said the 8 inch version seems targeted directly at Google's $229 Nexus 7, while the 10-inch tablet undercuts the price of Amazon's 8.9 inch Kindle Fire HDX.

Tech review site CNET said the Yoga tablets were reminiscent of the Sony Tablet S and Xperia Tablet S, with their cylindrical edge offering a solid handle.

They "do feel well-balanced and light when held this way -- especially true with the lighter 8-incher -- and the cylinder gives your hands something smooth and easy to grip."

"Overall the tablets feel pretty well-built," it added.

The new Lenovo tablets were unveiled exactly a week after Apple revved up its iPad line as it moved to fend off rivals which have eroded its dominance in the sizzling tablet market.

A slimmer version of its top-selling full-size tablet computer, dubbed the "iPad Air," was announced last week along with a revamped iPad Mini with an improved high-definition display.