China’s Ministry of Commerce said on Saturday ‌it had issued an injunction to block U.S. sanctions imposed on five Chinese refiners accused of buying Iranian oil, according to state news agency Xinhua.

The ministry ‌named the five as Hengli Petrochemical (Dalian) Refinery, ​and so called 'teapot' refineries Shandong Jincheng Petrochemical Group, Hebei Xinhai Chemical Group, Shouguang Luqing ⁠Petrochemical and Shandong Shengxing Chemical.

In April, the ​U.S. Treasury imposed sanctions on Hengli Petrochemical, accusing it ⁠of buying billions of dollars in Iranian oil, in an escalation of Washington's long-running effort to curb Tehran's oil ‌revenue.

The Trump administration last year imposed ​sanctions on the other ‌four refineries named by the ministry, among others.

The U.S. ‌sanctions violate "international law and the basic norms of international relations," the ministry said.

As a result, the ⁠ministry said, it had ‌imposed an injunction.

"The ⁠injunction stipulates that the United States cannot recognize, implement, or ⁠comply ⁠with the sanctions imposed on the aforementioned five Chinese companies," added ‌the ministry.

The sanctions created some hurdles for the refiners, including difficulties receiving crude and having to sell refined ‌products under ​different names. ‌Teapots account for a quarter of Chinese refinery capacity, operate with narrow and sometimes negative ​margins and have been squeezed recently by tepid domestic demand.