China strongly opposes U.S. sanctions on a Chinese energy firm accused of violating curbs on Iran's oil sector levied over Tehran's nuclear program, its foreign ministry said on Tuesday.

The United States sanctioned the company, Zhuhai Zhenrong Co. Ltd., because it "knowingly engaged in a significant transaction for the purchase or acquisition of crude oil from Iran," U.S. Secretary of State Mike Pompeo said on Monday.

Beijing firmly opposed the sanctions, foreign ministry spokeswoman Hua Chunying said, adding that China's cooperation with Iran was normal under international law.

"We urge the U.S. to correct this wrongdoing and stop its illegal sanctions on companies and individuals," she told reporters at a daily briefing.

"The U.S. has neglected the legitimate rights of all countries and randomly applies sanctions, this is in violation of international law," Hua added.