Last month, Beijing restricted exports of tungsten and seven categories of rare earths as part of its response to US President Donald Trump's sweeping tariffs on Chinese goods.

In 2024, China banned exports to the United States of gallium, antimony and germanium -- key components in semiconductors -- as well as certain types of graphite used in electric vehicle batteries.

China dominates the global supply chains for rare earths, essential in the manufacture of smartphones, wind turbines, military equipment and many other goods.

Resecuring access to the materials is reportedly a priority for Washington as the world's two largest economies hold trade talks this weekend.

China's commerce ministry said in a statement Friday that "some foreign entities have colluded with domestic illegal personnel, constantly innovating their smuggling export methods, and trying to evade crackdowns".

It added that several government departments would jointly combat "typical evasion methods such as false reporting, concealing smuggling and 'third country' transhipment".

"Avoiding the illegal flow of strategic minerals, curbing the momentum of smuggling and effectively safeguarding national security... has become an urgent and important task," the statement said.

In April, South Korean media reported that the Chinese government had warned several South Korean companies that they risked sanctions if they were found to have violated Beijing's export control restrictions by shipping products containing Chinese rare earths to US defence firms.