China's Ministry of State Security says it is cracking down on alleged smuggling of rare earths materials that it says threaten national security.

China's shipments of rare earth magnets to the United States jumped sharply in June. The rebound came after months of disruption and signaled renewed momentum in critical mineral trade between the two countries.

Total cargoes of the magnets rose to 3,188 tons last month, according to Chinese data on Sunday, more than double volumes of 1,238 tons in May in the midst of China’s curbs.