The HTC Butterfly features a 5-inch screen with a pixel density of 440 ppi (pixels per inch) and full 1080p HD resolution, compared to the iPhone 5's 4-inch screen at 326 ppi at a lower resolution.

"We are confident that HTC Butterfly will set a new example for high-end smartphones," chief executive Peter Chou said at the launch in Taipei.

The new model, which is slimmer and curvier, is equipped with the latest 1.5 GHz Quad-Core S4 processor that allows users to surf the Internet and stream HD movies to their TV wirelessly at the same time, HTC said.

Its photo-taking and audio functions are also enhanced, with an ultra-wide front angle lens as well as a built-in amplifier for higher sound quality, the company said.

HTC sells its own smartphones and also makes handsets for a number of leading US companies, including Google's Nexus One.

The company has recently unveiled a new series of smartphones as it faces intense competition from Apple and South Korea's Samsung and seen its third quarter profit tumble 79.1 percent year-on-year.

HTC and Apple were locked in more than 20 patent lawsuits worldwide until the two firms reached a global patent settlement last month.

The world's leading technology firms have routinely pounded each other with patent suits.