Tesla CEO Elon Musk said on Tuesday that the production of its Optimus humanoid robots had been affected by China's export restrictions of rare earth magnets.

He said China wants assurances that its rare earth magnets are not used for military purposes, adding that the automaker is working with Beijing to get an export license to use rare earth magnets.

Hong Kong-listed shares of JL Mag Rare-Earth surged 13% in afternoon trading.