A major port in northern China has reportedly banned coal imports from Australia in a sign that Beijing may be flexing its economic muscles and warning nations not to bar its next-generation wireless technology.

The indefinite coal restrictions at Dalian started this month and are part of an overall plan to cap imports into the customs region this year, Reuters reported, citing an unnamed Dalian Port Group official.

China's foreign ministry wouldn't say if it was specifically targeting Australia, only that it regularly inspects coal imports for environmental reasons, international wire service Bloomberg said.

The move may be a shot across the bows of Australia, which last year followed the US in banning Chinese telecommunications giant Huawei Technologies Co from its 5G network on security concerns.


China has said the concerns are unreasonable and warned other countries of unspecified consequences if they follow suit in blocking Huawei equipment.

While Dalian only takes about 2 per cent of Australia's coal exports, such a ban would mark a deterioration in often strained relations between the key trading partners.

The Australian dollar fell as much as 1.1 per cent, the most in two weeks, to around 0.7086 on Thursday after the Reuters report.

Meanwhile, China's biggest traded mining company, China Shenhua Energy Co, rose more than 4 per cent.

Asked directly about the report on Thursday, foreign ministry spokesman Geng Shuang told reporters in Beijing that China examines imported coal to protect the environment.

He didn't say whether China was targeting Australia specifically. Trade Minister Simon Birmingham said Australia's ambassador to Beijing was seeking to "urgently clarify" the veracity of the report.

China, which has a history of using trade as leverage, has been seeking to counter resistance in several nations to using Huawei in 5G networks.

Its ambassador to Canada this week warned that excluding the company will have repercussions. New Zealand, which has also barred Huawei, has sought to downplay concerns that China is now turning a cold shoulder.

- Additional reporting from Bloomberg