BEIJING—China on Thursday promised to take action against U.S.-sanctioned companies if it sees “solid evidence” they illegally helped North Korea, while cautioning against the imposition of foreign laws on Chinese citizens.

Foreign Ministry spokesperson Hua Chunying told reporters she had no information on entities targeted by new U.S. sanctions, but those violating UN Security Council resolutions or Chinese law would be dealt with strictly.

“If solid evidence shows there are violations ... I can reassure that China will deal with it strictly, in accordance with the law,” Hua told reporters at a regularly scheduled briefing.

The Trump administration announced sanctions Wednesday on North Korean business networks in China and Russia as it pushed to cut off revenues for the increasingly isolated nation’s nuclear program.

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The Treasury Department’s Office of Foreign Assets Control also targeted five North Korean shipping companies and six of its vessels. That’s part of an intensified effort by Washington to interdict ships that help the North evade sanctions.

The sanctions have been tightened significantly in the past year as Kim Jong Un’s government works to perfect a nuclear weapon that can threaten the U.S. mainland. While Beijing and Moscow have supported UN restrictions, they bristle at Washington imposing unilateral sanctions to bolster the pressure campaign.

“We firmly oppose ‘long-arm jurisdiction,’ the imposition of other countries’ domestic laws on Chinese entities and individuals,” Hua said at Thursday’s briefing.

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