In March this year, a new firm appeared in Turkey's corporate registry. Azu International described itself as a wholesale trader of IT products, and a week later began shipping U.S. computer parts to Russia.

Business was brisk, Russian customs records show. The United States and the EU had recently restricted sales of sensitive technology to Russia because of its Feb. 24 invasion of Ukraine, and many Western tech companies had suspended all dealings with Moscow.

Co-founded by Gokturk Agvaz, a Turkish businessman, Azu International stepped in to help fill the supply gap. Over the next seven months, the company exported at least $20 million worth of components to Russia, including chips made by U.S. manufacturers, according to Russian customs records.