Beginning in 2010, Mr. Zanjani, who declined to be interviewed for this article, told the magazine and, in a separate meeting, the semiofficial Iranian Students’ News Agency that he used a spider web of 64 companies in Dubai, Turkey and Malaysia to sell millions of barrels of oil, earning $17.5 billion in desperately needed foreign exchange for Iran’s Oil Ministry, Revolutionary Guards and central bank.

Image Babak Zanjani began his career selling sheepskins and became a critical actor in Iran’s effort to evade sanctions on oil sales. Credit... Reza Moattarian

“The central bank was running out of money,” he said in the Aseman interview, published last week. In 2010, “they asked me to bring their oil money into Iran so the system could use it,” Mr. Zanjani said of Iran’s political establishment. “So that is what I did.”

Among the companies he was controlling were a Turkish airline, various financial institutions and a fleet of oil tankers, many of which he put to use in evading the sanctions.

He devised a scheme to disguise the origins of Iranian oil and sell it on the open market, transferring millions of barrels from tanker to tanker — often in a little-known harbor on the tiny Malaysian island of Labuan in 2012, the European Union charges. In total, he said, he sold 24 million barrels of oil to buyers in Singapore, Malaysia and India and then laundered the money through Malaysian First Islamic Bank, which is now on all the sanctions lists.

“This is what I do — antisanctions operations,” Mr. Zanjani said. “I am a businessman who has done his job well. Since I was placed under sanctions they haven’t managed to sell even three million barrels of oil.”

Mr. Zanjani is sparse with details about his early business dealings, but admitted in the magazine interview that he had gotten his big break in 1999, when he became the driver for Mohsen Nourbaksh, the chief of Iran’s central bank. Mr. Zanjani displayed a talent for money changing, and said he was quickly earning around $17,000 a day — his cut on all the currency deals.