Prices of iron ore slumped more than 3% to their lowest in six weeks on Wednesday, after China's top steelmaking city of Tangshan issued a second-level smog alert that requires mills to further limit operations.
Mining behemoths BHP Group and Rio Tinto lost 3.3% and about 3%, respectively, weighing on the benchmark.
The New Zealand benchmark closed 0.3% lower at 11,141.86 with payments platform provider Pushpay Holdings Ltd declining more than 3%.