Japanese trading company officials say China's exports to Japan of rare earth elements — which are crucial for advanced manufacturing — have been halted.

The two officials said Friday the shipments were suspended on Tuesday. They declined to be named as they were not authorized to talk to the media. The move comes amid escalating tensions between China and Japan over a territorial dispute.

Beijing has repeatedly demanded Tokyo release a Chinese fishing boat captain who was arrested after a collision with two Japanese coast guard vessels near disputed islands in the East China Sea. China's Premier Wen Jiabao on Tuesday threatened action against Japan if it does not immediately release the captain.

Rare earth are metallic elements crucial for superconductors, computers, hybrid electric cars and other high-tech products.