"China expresses strong opposition and deplores such sanctions by the US side. (...) It has suppressed Chinese enterprises based on its domestic law. China's cooperation with Iran within the international framework is legitimate and legal, thus should be respected and protected," Foreign Ministry spokesperson Geng Shuang as saying by Xinhua news agency.
Washington imposed sanctions on cargo transport firms Cosco Shipping Tanker and Cosco Shipping Tanker Seaman - subsidiaries of Cosco, the sector's largest state-owned company in China - as well as China Concord Petroleum, Kunlun Shipping, Kunlun Holding and Pegasus 88 Limited.
Assets of these companies under US jurisdiction now remain frozen, and financial transactions with them are prohibited.
"The US ignores the legitimate and legal interests and rights of all parties and wantonly wield the sanctions stick," Geng said, terming these actions as "bullying practices", and rejected the sanctions for their "unilateral" nature.
"We urge the US to correct its wrongdoing and China has and will continue to take necessary measures to safeguard the legitimate rights of our own enterprises," the spokesperson underlined.
US Secretary of State Mike Pompeo announced these sanctions on Wednesday during a speech in which he accused the affected companies of knowingly transporting oil from Iran.
"We are telling China, and all nations: know that we will sanction every violation," Pompeo said at a conference on the sidelines of the United Nations General Assembly (UNGA) in New York.
On Tuesday, US President Donald Trump, during his intervention before other international leaders at the UNGA, called for more pressure on Tehran and made it clear that his country is not going to roll them back.
"As long as Iran's menacing behavior continues sanctions will not be lifted. They will be tightened,'' Trump had said.
Trump had for weeks hinted at the possibility of meeting with Iranian leader Hassan Rouhani, which would have been historic.
However, all such possibility disappeared with recent attacks on Saudi oil refineries, for which Washington blames the authorities in Tehran.
( With inputs from IANS )