In a terse statement, China’s foreign ministry spokesman Geng Shuang said the government had always fully and thoroughly enforced UN resolutions on North Korea, and absolutely did not allow any of its citizens or companies to contravene them.

“China resolutely opposes the US side enacting unilateral sanctions and ‘long-armed jurisdiction’ in accordance with its domestic law against Chinese entities or individuals,” it said.

“We have already lodged stern representations with the US side about this issue, and demand the US side immediately stops such relevant mistaken actions to avoid harming bilateral cooperation in the relevant area.”

The US treasury department said in a statement on its website that it had sanctioned one person, 27 companies and 28 ships. The actions block assets held by the firms and individuals in the United States and prohibit US citizens from dealing with them.

Two Chinese shipping firms – Shandong province-based Weihai World-Shipping Freight and Shanghai-based Shanghai Dongfeng Shipping Co – were among the companies on the sanctions list, which also included entities based elsewhere on China’s mainland as well as in Hong Kong, Taiwan, Singapore and North Korea.

The only person on the list was identified as 61-year-old Taiwanese businessman Tsang Yung-yuan, the founder of Taipei-based Yu Feng Chin Enterprise Company.

“Tsang has coordinated North Korean coal exports with a Russian-based North Korean broker, and he has a history of other sanctions evasion activities,” the US treasury said.

The statement also identified Taiwan-based Pro-Gain Group Corporation and Taiwan and Marshall Islands-based Kingly Won International Co. A check of the addresses provided by the treasury connected both companies to Yu Feng Chin, which was set up by Tsang and registered with the Taipei city government in 2013 with capital of just NT$100,000 (US$3,400).

In response, judicial authorities in Taipei said they had begun an investigation into the allegations against the businessman.

“Shihlin Prosecutors Office has been assigned to initiate an investigation into the case, but until they have a full and clear picture about it, it is still not the time to summon any party involved for questioning,” Chen Ming-tang, Taiwan’s deputy justice minister said.

The island’s justice ministry was seeking help from the foreign ministry and national security bureau to get fuller information from the US, he said, adding that anyone found to have violated the UN sanctions would be subject to prosecution under the terrorism financing prevention act, which is punishable by imprisonment and a freezing of assets.

Local television companies caught Tsang leaving the offices of Yu Feng Chin on Friday. All calls to the company since then went unanswered.

Taiwan banned all trading with North Korea in September, in line with the UN sanctions, although the island is not a member of the United Nations.

Last month, Taiwanese authorities banned all financial dealings with Kaohsiung-based businessman Chen Shih-hsien, who was accused in December of selling oil to North Korea, and froze his companies’ bank accounts.

Late last month, prosecutors in Kaohsiung detained businessman Chiang Kuo-hua – the son of a former high court judge – after questioning him over his alleged role in selling 40,000 tonnes of North Korean anthracite coal – its purest form – to Vietnam.

Earlier this month, they questioned another Kaohsiung-based businessman, 56-year-old Chuang Chin-hung, over the alleged sale of 7,000 tonnes of diesel oil to North Korea in December, prosecutors said. He was released on NT$2 million bail and will face further questioning.

Additional reporting by Reuters