China firmly opposes illegal unilateral sanctions that have no basis in international law and are not authorized by the United Nations Security Council, a Chinese Foreign Ministry spokesperson said at a regular press briefing on Monday.

Responding to US sanctions imposed on three Chinese companies over allegations that they assisted Iran's military activities, Chinese Foreign Ministry spokesperson Guo Jiakun said China had repeatedly made clear its position on the Iran issue.

"The pressing priority now is to make every effort to prevent renewed conflict, rather than maliciously associating the situation with and smearing other countries," Guo said.

China has consistently required its companies to conduct business operations in accordance with laws and regulations, Guo said, adding that China will firmly safeguard the legitimate rights and interests of its companies.