China on Wednesday voiced its "firm opposition" to United States sanctions against Chinese enterprises and individuals.

The U.S. has accused a Chinese businessman of violating sanctions against Iran by selling missile parts to it. Media reports say the U.S. State Department has offered a bounty of five million U.S. dollars for information leading to businessman Li Fangwei's arrest or conviction.

"The Chinese side is firmly opposed to the United States' unilateral sanctions according to its domestic law over Chinese enterprises and individuals," Chinese Foreign Ministry spokesman Qin Gang said.

The sanctions will harm cooperation between the two countries on nonproliferation, said the spokesman. The Chinese government attaches great importance to nonproliferation and will punish any behavior that goes against nonproliferation laws.

"The U.S. concern should be addressed through law-enforcement cooperation with China on nonproliferation," Qin said, urging the U.S. side to "come back to the normal track of nonproliferation."