The Treasury Department imposed sanctions Wednesday on a Chinese refinery accused of purchasing more than $1 billion worth of Iranian oil, saying the proceeds help finance both Tehran's government and Iran's support for militant groups.

The sanctioned refinery in China's Shandong province received dozens of shipments of crude oil from Iran worth more than $1 billion, the Trump administration said. Some of the petroleum came from a front company for Iran's paramilitary Revolutionary Guard, U.S. authorities said.