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What is described as the world's biggest ultra-definition (UD) TV has been released by LG Electronics.

It sports an 84in (213cm) screen, smaller than a 90in model made by Sharp, but LG boasts support for 4K, a more advanced picture format.

LG's screen offers 8 million pixels per frame, four times the resolution of 1080p high-definition displays.

The firm sees this technology as a key marketing tool to help challenge market leader Samsung.

Toshiba already offers a smaller 55in 4K screen, and Panasonic a 20in model. Sony and Samsung are also developing their own devices.

However, LG's 25 million-won ($22,010; £13,940) price tag is likely to dissuade many from investing in its technology at present.

"The 4K display market is still in its infancy but it was important for LG to claim a stake in this space," said the chief executive of LG Electronics 91Èȱ¬ Entertainment, Havis Kwon.

The South Korean company is the second-largest seller of flatscreen television screens, and is known to compete with its domestic rival, Samsung, for bragging rights.

Earlier this year it sought to upstage its rival by showing off the world's largest OLED (organic light-emitting diode) at the Consumer Electronics Show trade show in Las Vegas. But when Samsung heard about the news it shipped an identically sized model to the event.

One analyst said that sales of the latest release were likely to be limited, but it provided an indication of where the industry was pointed.

"4K is a technology that is an evolutionary step that - maybe a long way down the line - will be the successor to today's HD televisions," said Daniel Simmons from IHS Screen Digest.

"It's a step up in image quality, offering the opportunity to have cinema-quality resolution in the home and is a noticeable improvement.

"But it is worth recognising that many people only upgraded their televisions from CRT [cathode ray tube] models in order to have a larger flatscreen model - the high-definition feature was not the primary motivator.

"4K allows people to have even bigger screens in their homes and it may be the screen size, rather than the resolution itself, that makes it attractive."

LG's 84in model has initially been released in South Korea ahead of its launch elsewhere in the world in September. It will also show off the device at the IFA tech trade show in Berlin at the end of August.