The decline in revenues was primarily attributed to lower sales of premium devices and expenses related to business structure improvement activities, the company said.
The company reported an operating loss of KRW 436.4 billion (USD 389.4 million).
LG shipped 13.5 million smartphones in the quarter, with North America reporting a 14 percent increase in sales from the second quarter.
LG will focus on increasing the sales of its new LG V20 smartphone and mass-tier K and X series and finalizing business structural improvements in the mobile division, the company said in a statement.
Overall LG Electronics reported sales of KRW 13.2 trillion (USD11.8 billion) and operating income of KRW 283.2 billion (USD 252.7 million), for the quarter.
The strong performance of its Home Appliance & Air Solution business and increased profitability in Home Entertainment has helped it offset sales declines and operating losses from Mobile Communications, company officials said.