BEIJING, May 11 (Reuters) - China voiced strong opposition on Monday to U.S. sanctions for three China-based companies that Washington claimed enabled Iran's military operations, calling the curbs illegal and unilateral.

"We have always required Chinese enterprises to conduct business in accordance with laws and regulations, and will firmly safeguard the legitimate rights and interests of Chinese enterprises," spokesperson Guo Jiakun told a regular press briefing.

"The pressing priority is to prevent by all means a relapse in fighting, rather than using the war to maliciously associate and smear other countries."

(Reporting by Liz Lee and Shi Bu; Editing by Clarence Fernandez)