Sydney/Canberra | A top Chinese Customs official has warned authorities would strengthen the "import supervision" on Australian coal and other products in the latest sign that Beijing is using economic retaliation to pressure the Morrison government.

Coal traders in China on Tuesday confirmed reports that China has told some of its state-owned steel makers and power plants to stop importing Australian coal, although it was unclear how damaging those instructions would be as many buyers had already hit their import quota limits.