SEOUL (AFP) - Samsung Electronics said Thursday its third-quarter net profit plunged nearly 50 per cent from a year ago amid growing competition from Chinese rivals in the increasingly saturated market.

Net profit for the South Korean electronics giant amounted to 4.22 trillion won for July to September - the lowest such figure since the fourth quarter of 2011.

Operating profit also dropped 60 per cent from a year ago to 4.06 trillion won, slightly less than its earlier forecast of 4.1 trillion won.

Sales also tumbled about 20 per cent to 47.4 trillion won, Samsung said in a statement.

"Despite a marginal increase in sales volume, the (mobile unit) saw earnings fall for two consecutive quarters, as smartphone average selling price declined due to reduced prices for older models and increased sales of middle-end smartphones," it said.

Samsung - the world's largest manufacturer of smartphones and TVs - earlier reported a 20 percent drop in its second-quarter net profits as its key handset business faced slowing demand in lucrative advanced markets and intensifying competition from cheap Chinese device makers.