Hong Kong CNN Business  — 

The trade fight between China and Australia appears to be escalating, with Beijing reportedly placing new restrictions on imports of Australian coal.

Australian Trade Minister Simon Birmingham on Tuesday said he was “deeply troubled” by new reports in Chinese state media that the country’s top economic planner has effectively banned certain coal imports from Australia. The Global Times, a state-run tabloid, reported last weekend that the country’s National Development and Reform Commission has given power plants approval to buy overseas coal without restrictions — except from Australia.

If true, the reports “would indicate discriminatory trade practices being deployed by Chinese authorities,” Birmingham told Australia’s Radio National. China has already banned or slapped tariffs on a range of other Australian exports.

Asked by reporters on Tuesday about the reports, China’s Ministry of Foreign Affairs directed questions to the “relevant authorities.” But spokesman Wang Wenbin did acknowledge that “Chinese authorities have recently taken relevant measures against certain Australian products exported to China in accordance with the law and regulations.”

Australian Prime Minister Scott Morrison, meanwhile, told reporters in Australia on Tuesday that the government is “seeking clarification” on the reports, adding that the country has yet to hear from the Chinese government. He called reports that China is blocking Australian coal a “bad outcome for the trading relationship” between the two nations.

Relations have been deteriorating since April, when Morrison called for an international inquiry into the origins of the coronavirus pandemic. Beijing at the time called that move “political manipulation.”

In the months since then, China has slapped Australian winemakers with heavy tariffs, and banned or taxed exports of other products, including beef and barley.

Morrison said Tuesday that Australia sends 4 billion Australian dollars ($3 billion) worth of thermal coal to China each year, adding that Japan is a bigger market than China for those exports. Thermal coal is primarily used to generate power. In total, Australia exported some 14 billion Australian dollars ($10.5 billion) worth of coal to China in the 2018-2019 fiscal year.

But the impact on trade of any move against Australian coal is tough to gauge. Australian media pointed out weeks ago that hundreds of millions of dollars worth of coal was already being held off the coast of China, an indication that Beijing was at least informally putting pressure on Australia’s vital mining industry.

“This opacity makes it hard to say how much of an escalation this news is,” said Sean Langcake, senior economist at Oxford Economics, noting the existing disruptions in thermal coal trade. “These have clearly not been resolved, and it’s hard not to see this news as a further deterioration.”

Investors in Australia’s major coal producers are taking the reports as a bad sign. Shares in Coronado Global and Yancoal Australia each plunged more than 8% in Sydney on Tuesday. Whitehaven Coal dropped nearly 6% on Tuesday, and is down 10% so far this week.

Analysts at ANZ Research wrote in a research note that the Chinese reports confirm “what has been assumed ever since reports of import restrictions on coal from Australia emerged in October.” They noted that while China has been an important market for Australian thermal coal — it made up nearly a third of Australia’s total exports in 2018 — that market share has been falling ever since.

“Australian exporters have found additional buyers in South Korea, Vietnam and Japan,” the analysts wrote. “As such we see Australia’s thermal coal exports holding up relatively well, despite the Chinese ban.”

Economists have noted that other mining materials, predominately iron ore and coking coal used in steelmaking, make up a particularly large share of Australian exports. Langcake told CNN Business earlier this month that restrictions on such exports are unlikely, given how reliant China’s steel industry is on them. (Iron ore prices have been trading at the highest levels in years, in part because of demand rising as China recovers from the pandemic.)

— Angus Watson contributed to this report.