South Korea's Samsung posted Friday an 18 percent drop in operating profit in the fourth quarter as slowing sales of high-end smartphones hit the electronics giant.

Operating profit stood at 8.3 trillion won ($7.8 billion), down 18 percent from the July-September period, marking the company's first quarterly profit decline in two years.

The fourth quarter figure was also down 6.0 percent from a year ago.

The world's top maker of mobile phones and TVs said earnings were lower than expected, due to a "negative currency impact" of 700 billion won and a "significant one-off expense" of 800 billion won.

"For the first quarter it will be challenging for Samsung to improve its earnings as the weak seasonality of the IT industry will put pressure on demand for components and TV products," it said.

The latest earnings result ended the company's long run of record quarterly profits on the back of surging sales of its flagship Galaxy series smartphones.

The mobile division posted a quarterly operating profit of 5.47 trillion won, down 2.8 percent from the third quarter.

The company statement said the division's earnings were down due to seasonally increased marketing costs, as well as the one-off expense.