Hebei Xinhai Chemical Group, Ltd, a so-called teapot refinery in Hebei Province, was the main target of yesterday’s action.

Treasury said in a statement that the refinery has received multiple shipments of Iranian oil worth hundreds of millions of dollars from vessels operating as part of a shadow fleet.

Along with the refinery, the treasury also sanctioned three firms for operating a terminal at Dongying Port, which the US alleges took several shipments of Iranian oil since last year.

The department also sanctioned six vessels and two Indian-national ship captains for allegedly transporting Iranian oil.

Hebei Xinhai is the third Chinese teapot refinery the US has sanctioned after it took action against one in Shandong Province in March and a second in April.

The company also owns Singapore-based oil broker Xing AO Energy Pte Ltd, which treasury also sanctioned.

The increased attention on these independent refiners in Shandong, which are the biggest buyers of Iranian crude, is part of a “maximum pressure” campaign against Tehran ordered by President Donald Trump and carried out by the treasury, which implements the bulk of US sanctions.

The US “remains resolved to intensify pressure on all elements of Iran’s oil supply chain to prevent the regime from generating revenue to further its destabilising agenda,” treasury secretary Scott Bessent said in a statement.

Oil revenue is crucial to Tehran and a lifeline for Shandong’s private processors.

In the past, the trade has been facilitated by ship-to-ship transfers in the waters off Malaysia to mask the origins of the cargoes.

A crackdown by the US, as well as China, since January has snarled that supply chain.

Traders have since turned to privately run berths to receive the cargoes.