The United States has imposed sanctions on four individuals (including a Syrian businessman, one Russian and a Cypriot national) and six entities accused of helping Syria to bypass international sanctions and purchase oil from Islamic State.

As reported by The Financial Times, the US Treasury department one of the men is Kirsan Ilyumzhinov, the head of the world chess federation. Another is George Haswani, a Syrian national, and his company, Hesco Engineering and Construction. The Treasury said Haswani, who was placed on an EU sanctions list earlier this year, “serves as a middleman for oil purchases by the Syrian regime from IS”.

The Treasury also sanctioned a group of Russian and Cypriot businessmen and companies for allegedly helping the Syrian central bank evade international sanctions.

While US officials have often claimed the Syrian government purchases oil from Islamic State, the November 25 announcement represents the most direct accusation yet by the administration about the links between the Syrian regime and IS, according to The Financial Times.

“The United States will continue targeting the finances of all those enabling Assad to continue inflicting violence on the Syrian people,” said Adam Szubin, acting under secretary for terrorism and financial intelligence, in a statement.

The four individuals and six entities listed by the Treasury will have any assets in the US frozen and will be barred from doing business with US companies or individuals.