LG Electronics unveiled Monday the latest version of its flagship smartphone, boasting a higher resolution screen aimed at gaining a technical edge over bigger rivals like Samsung.

The Optimus G Pro -- the newest version of the Optimus G series and the first LG smartphone offering a full high-definition (HD) screen -- will hit stores at home Wednesday, the South Korean firm said.

The new handset is powered by Android software and measures 15.2 centimetres (5.98 inches) long and 7.6 centimetres wide. It goes on sale in Japan and North America in the second quarter.

The Optimus G Pro features a 5.5-inch display that packs over 2 million pixels, or twice as many as smartphones with ordinary HD screens, offering brighter and clearer images.

Global handset makers like Taiwan's HTC and Sony of Japan have recently rolled out models boasting full HD screens -- most commonly used for TVs -- to gain an edge in the increasingly competitive smartphone market.

Samsung Electronics, the world's top maker of both smartphones and mobile handsets in general, is also expected to unveil a new full-HD version of its headline Galaxy S model.

"With smartphones getting bigger and bigger, its visual function becomes ever more important," LG said in a statement. "An ability to offer high-resolution images is paramount."

LG, the world's number two flat-screen TV producer and the fifth biggest phone maker, has struggled for years in the rapidly-growing smartphone market, with its Optimus series lagging far behind Apple's iPhone or the Galaxy S.

But heavy promotion of new models saw LG's smartphone sales in the fourth quarter of 2012 surge 56 percent from a year ago to a record 8.6 million units.