SEOUL: World's largest smartphone maker Samsung Electronics Co is heading for its roughest quarter in years amid rising competition from Apple Inc and China's Xiaomi Corp.

Analysts have been cutting their profit estimates almost daily, with at least 26 of 42 tracked by Bloomberg reducing their estimates in the past four weeks.

Operating profit for the third quarter is projected to plunge 47 per cent, while sales are projected to fall 15 per cent, according to the average analyst estimates. Both are the steepest declines since at least 2009.

Samsung is fighting to retain its dominance after Apple introduced bigger-screen iPhones and Xiaomi began selling its low-cost devices in more overseas markets.

It moved up the release date for its Galaxy Note 4 smartphone to the end of last month, meaning device sales will aid third-quarter results.

"We all know Samsung's third-quarter earnings will be pretty ugly," Claire Kim, analyst at Daishin Securities Co, said by phone.

"The earlier release of its new phones could be reflected in its third-quarter earnings; it could give them a slight boost."

Samsung has lost about 17 per cent of its market value this year, or about US$32 billion (RM104 billion).

"Samsung wanted to release the Note 4 in China ahead of Apple to give an earlier splash," said Greg Roh, analyst at HMC Investment Securities Co.

"Although it's the very-last minute release in September, it will definitely contribute to its third-quarter earnings."

"The most important thing for Samsung now is to protect its fast-falling market share, especially in China," said Daishin Securities' Kim. Bloomberg