SEOUL (Reuters) - Three deputies to the head of Samsung Electronics's mobile division are leaving, a person with knowledge of the matter said on Thursday, as the world's largest smartphone maker faces a rapid decline in profit.

The person, who declined to be named due to the sensitivity of the matter, said the executives directly report to division chief J.K. Shin, who this week retained his post despite sagging smartphone sales and expectations the company will see its worst annual profit in three years in 2014.

The departures included global marketing chief D.J. Lee, the source said, confirming earlier media reports.

Samsung Electronics declined to say if any executives were leaving the company as it announced its annual reshuffle for executive-level staff.

But the announcement showed Samsung had made 165 executive-level promotions, the lowest number in at least four years, underscoring the strains the South Korean company is under.

"Shin was given another chance, given his past contributions, but he will definitely continue to feel the pressure going forward," said IBK Securities analyst Lee Seung-woo ahead of Samsung Electronics' staff announcement.

Samsung's share of the smartphone market has fallen year-on-year for the last three quarters, squeezed by Chinese rivals like Xiaomi Technology Co Ltd at the low-end and Apple Inc's iPhones in the premium segment.

Samsung Electronics is expected to announce its annual business reorganisation plan by next week.

The company has kept mum about the details but the Joongang Ilbo newspaper reported earlier that Samsung will reduce executive-level positions for its mobile communications business by 25 percent. Other media reported the company could hive off its medical equipment business.

Samsung earlier this week said it will sell its fibre optics business to U.S. speciality glass maker Corning Inc, its second exit from a non-core business this quarter.