SEOUL (REUTERS) - South Korea's Samsung Electronics on Tuesday (Jan 8) estimated a decline in quarterly operating profit for the first time in two years, as a slowing Chinese economy erodes demand for its chips and handsets.

Weaker earnings at the world's biggest maker of smartphones and semiconductors adds to worries for investors already on edge after Apple Inc last week lowered its quarterly sales forecast, in a rare move, citing poor iPhone sales in China.

Samsung, in a regulatory filing, estimated profit at 10.8 trillion won (S$13.1 billion) for October-December last year, down 29 per cent from the same period a year earlier. It was also sharply below the 13.2 trillion won average of 26 analyst estimates in a I/B/E/S Refinitiv poll.

It also estimated a 11 per cent on-year revenue decline at 59 trillion won.

Samsung will disclose detailed earnings later in January.

Analysts expect Samsung's profit to decline through 2019 as weakness in China persists, Refinitiv data showed.

Prices for DRAM chips, which provide devices with temporary workspaces and allow them to multi-task, declined 10 percent in the fourth quarter, according to industry tracker DRAMeXchange.