Samsung Electronics on Friday flagged a 15 percent increase in 2015 Q4 operating profit, rounding off a year in which the world's largest smartphone producer struggled with intense competition from arch-rival Apple and cut-price Chinese competitors. 

In an earnings estimate, the South Korean tech giant predicted an operating profit of 6.1 trillion won ($5.1 billion) for the October-December period, up from 5.4 trillion won a year earlier.