Western officials, security experts, and Iranian trading sources cited by the news agency said the Islamic Revolutionary Guard Corps (IRGC) now control up to half of the country's oil exports, up from around just a fifth three years ago.
The Islamic Republic, despite harsh sanctions by the United States and its allies, generates more than $50 billion a year in oil revenue - a key lifeline for foreign currency.
Iran's entire oil industry has now fallen under the sway of the Revolutionary Guards, Reuters reported citing over a dozen interviewees, including the ships covertly transporting sanctioned crude to logistics and front companies facilitating oil sales.
China is Iran's top customer and China Haokun Energy, a front company operated by former Chinese military officials, remains an active conduit for the sales despite being slapped with US sanctions last year.
The sources, who requested anonymity due to the sensitivity of the topic, shared insights derived from intelligence documents and tracking ships linked to the IRGC.