China said on Monday it has lodged a formal protest with the US over a decision to impose new sanctions targeting Iran, which has affected a handful of Chinese companies and individuals, according to media reports.

The sanctions were imposed on Friday after Iran conducted a ballistic missile test. The curbs affect 25 people and entities allegedly involved in helping Iran develop its ballistic missile programme, or in supporting groups that the US considers terrorist, such as Lebanon’s Shiite Hezbollah militant group.

They include two Chinese companies and three Chinese individuals, who are now blocked from the US financial system or dealings with American companies. Foreign companies and individuals are also prohibited from dealing with them at risk of also being blacklisted by the United States.

On Monday, Chinese Foreign Ministry spokesman Lu Kang said that Beijing has lodged a formal protest, the Washington Post reported.

“We have consistently opposed any unilateral sanctions,” Lu told a regular news conference. “The sanctions will not help in enhancing trust among the different parties involved and will not help in resolving international problems,” Lu said.

China has close economic and diplomatic ties with Tehran, but also played an important role in a landmark 2015 deal to curb the nation’s nuclear programme.

Executives from the two Chinese companies included on the list denied doing anything wrong.

Yue Yaodong, an executive at Cosailing Business Trading Co in the eastern city of Qingdao, said his firm was “collapsing” with his account at the Agricultural Bank of China frozen, a shipping company refusing to accept his goods, and clients abandoning him.

“We have not done any business with Iran for three to four years,” he said. “There have been some Iranian customers coming to us asking prices, but we have not conducted real business. Go search the customs record.”

He said his company sells items for everyday use, as well as porcelain, hydraulic parts, and motors for treadmills, but said it was only a small, private firm.

“I am so lost, both the United States and China are sanctioning me,” he said. “There is no way to do business now, I don’t know what our little company did wrong.”

US relations with China have hit a distinctly rocky patch since Trump took office, with the new President seeing the government in Beijing as more of a threat than a partner.

China also protested in recent days about comments made by Defense Secretary Jim Mattis on a tour of Japan and South Korea.