The United States announced on Thursday new sanctions targeting around 50 individuals, companies, and vessels—mostly based in Asia—accused of facilitating the sale and transport of Iranian oil and gas, including several firms in the United Arab Emirates.

In a statement, the U.S. State Department said it had imposed penalties on about 40 additional entities, describing them as “some of the largest purchasers of Iranian petrochemical products by volume and value,” as well as executives of companies involved in the trade.

The latest move marks the fourth round of sanctions targeting independent Chinese refineries, according to the department, and includes UAE-based firms allegedly helping to enable Iran’s energy exports in violation of U.S. restrictions.