South Korea, the world's No.4 coal importer, is expected to import around 19.85 million tonnes of thermal coal for the first three months, down 19.2% year-on-year, according to Reuters calculations based on customs data and ship tracking data from Refinitiv Eikon.

That would be the country's lowest first-quarter imports since 2010 when it imported 19.55 million tonnes. Demand is normally high during the quarter, which covers the winter months, running at 24-26 million tonnes over the past three years.

The drop in imports comes after South Korea imposed tougher restrictions on coal-fired power from December through March, halting nearly half of the country's 60 coal power plants by March as part of efforts to improve air quality.

Meanwhile, analysts said the coronavirus outbreak had reduced demand for electricity as business and factory activity slows. South Korea has faced the region's biggest COVID-19 epidemic outside of China, with over 9,000 cases.

"We expect South Korea's overall power consumption to fall in light of growth pressures stemming from the COVID-19 outbreak," said Daine Loh, an analyst at Fitch Solutions.

South Korea's daily peak power demand has averaged 70,633 megawatts (MW) so far in the first quarter of 2020, down 3.5% from 73,224 MW a year earlier, according to data from Korea Electric Power Corp (KEPCO).

Coal power typically produces about 40% of South Korea's total electricity, followed by nuclear and gas power.

With reduced power consumption and demand in the midst of the coronavirus outbreak, coal power's share of total power generation is expected at nearly 39% in 2020, down from 40% in 2019, Loh said.

Coal could also face increased competition from gas-fired power on the back of lower oil prices, said Shirley Zhang, an analyst from Wood Mackenzie.

In the first three months of the year, South Korea's liquefied natural gas (LNG) imports are expected to grow 25.2% year-on-year to 12.9 million tonnes, Refinitiv data showed.

"Lower oil prices will keep the LNG price lower, which will support anti-coal policy moves and increase the economic incentives for it to potentially outcompete some coal generation if sustained low and long enough," Zhang said.

By Jane Chung