Samsung had said demand for both the flat-screen and curved-screen models of its new flagship Galaxy S6 smartphones was "much higher" than initially planned for but the sales suggest otherwise.

However, the company expects earnings to rise in the second quarter after posting its highest profit in three quarters in January-March, boosted by strong demand for its new Galaxy S6 flagship smartphones.

Samsung's renewed focus on design after a period of stagnation in its smartphone range appears to be paying dividends, with researcher Strategy Analytics saying the South Korean giant overtook Apple Inc as the world's top smartphone maker in the first quarter.

"Galaxy S6 sales have been going as well as expected, while demand for the Galaxy S6 edge have been better than anticipated," Samsung Vice President Park Jin-young had said.

Samsung's mobile division's January-March operating profit improved to a three-quarter high of 2.74 trillion won.