China protested on Tuesday after the United States lodged criminal charges and sanctions on Monday against a Chinese firm it accuses of being connected to Pyongyang's nuclear weapons program.
The Foreign Ministry said China objects to any country attempting to exercise jurisdiction over a Chinese entity or individual based on its domestic laws.
The company targeted by the US, the Dandong Hongxiang Industrial Development Co, is already being investigated by the public security authority, Chinese officials announced. The cross-border trading company is registered near the China-DPRK border.
A US Treasury release issued Monday said authorities there were sanctioning the company and four of its executives, including company head Ma Xiaohong.
The US accused them of violating US laws against supporting "weapons of mass destruction proliferators", and engaging in money laundering in the US and elsewhere in support of Pyongyang. Reuters reported that the US Department of Justice said it had filed criminal charges against the firm and executives.
In response, Foreign Ministry spokesman Geng Shuang said: "Any enterprise or individual found in breach of the regulations will be treated seriously.
"In this process, if necessary, we would like to embark on cooperation with the relevant country on the basis of mutual respect and equality." Geng said.
This month, the Public Security Department of Liaoning province confirmed that the company and the executives concerned are "suspected of serious economic crimes" and under investigation with "due evidence in place".
Geng reaffirmed Beijing's opposition to Pyongyang's developing nuclear weapons and its commitment to Korean Peninsula denuclearization.
"However, I want to stress that we oppose any country enacting so-called long-arm jurisdiction, using its own domestic laws against a Chinese entity or individual," Geng said. "We have already communicated this position to the US side."
Zhang Liangui, an expert on Korean studies at the Party School of the Central Committee of the Communist Party of China, said Washington's latest sanctions partly aim to "add pressure to the Chinese government". It expects Beijing to step up sanctions.
"As China has jurisdiction over the case, there is no liability for the Chinese government to respond to an improper request, if there is any, by the US government," Zhang said.
"The US, in the meantime, knows clearly that the existing sanctions against the DPRK will not be a success without China's cooperation, so it is navigating the case issue cautiously to avoid angering Beijing," Zhang added.