China has intensified a trade squabble with Iran by labelling iron ore from the Islamic republic as substandard.
The two countries are already engaged in a dispute over crude prices, which prompted China to halve its orders for Iranian crude intended for January delivery.
The commodities are Iran's top two exports to China, and Tehran will have been stung by a statement issued by the Chinese commerce ministry yesterday warning companies against importing Iranian iron ore.
Iranian ore is of poor quality and imports are fraught with delivery problems, the ministry said.
"We have received lots of complaints from domestic companies about fraud regarding iron ore imports," the ministry said.
Product has failed to reach clients in China, and Chinese businessmen have been physically attacked during visits to Iran, the ministry claimed.
The rebuke comes on the heels of news that Sinopec, China's biggest refiner, has cut Iranian imports for next month by more than half.
"I would consider this very similar to the crude oil import limitation by [the Chinese state trading company] Zhuhai Zhenrong," an iron ore analyst in Beijing told Reuters.
"First, the timing is perfect, just on the heels of oil import payment concerns a few days ago. And secondly, China also used commercial risks as the main reason."
Iran is the fifth-largest exporter of iron ore to China, which is also a major importer of Iranian crude. Iran produced about 3.56 million barrels of oil per day last month, according to Bloomberg News.