Oil prices rose for a second day on Tuesday as the U.S. imposed fresh sanctions on Middle Eastern producer Iran that increased concerns supply might tighten.

The U.S. on Monday imposed sanctions on dozens of people and oil tankers across China, the United Arab Emirates, India and other jurisdictions for allegedly helping to finance Iran and its support for militant groups that launch attacks against the U.

The measures name more than 30 companies, people and vessels both in Iran and elsewhere that underpin the country’s ‘shadow fleet.’