"The Syrian government is responsible for widespread brutality and violence against its own people," said Adam Szubin, acting under secretary for terrorism and financial intelligence, in a statement announcing the sanctions action.
"The United States will continue targeting the finances of all those enabling Assad to continue inflicting violence on the Syrian people."
The Treasury Department named four individuals and six entities for sanctions for their support of the regime of President Bashar al-Assad, "including a middleman for oil purchases by the Syrian regime from the Islamic State of Iraq and the Levant (ISIL)," another name for the Islamic State group.
The department highlighted "ongoing government of Syria ties to ISIL."
Sanctions were imposed on George Haswani, a Syrian national, and his company, HESCO Engineering and Construction Company.
"Haswani is a Syrian businessman who serves as a middleman for oil purchases by the Syrian regime from ISIL. HESCO is a Syrian engineering and construction company that operates energy production facilities in Syria, reportedly in areas controlled by ISIL," the Treasury Department said.
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The European Union placed Haswani on its blacklist last March.
Also sanctioned Wednesday was Kirsan Ilyumzhinov, a wealthy Russian businessman and president of the World Chess Federation, and Mudalal Khuri, who "owns or controls" five of the entities designated.
Similarly the bank that Ilyumzhinov "owns or controls" Russian Financial Alliance Bank, also was sanctioned. Ilyumzhinov is linked to financial transactions involving Khuri-associated companies.
Other sanctions targets include Primax Business Consultants Limited and Belize-based Kremsont Commercial Inc.
The sanctions forbid US individuals or entities from doing any business with those on the blacklist, restricting their access to international financial networks crucial to doing business.Oil revenues are a major financial support for the Islamic State group.
The jihadists have seized swaths of territory in Syria and Iraq and sold crude oil from seized refineries on the black market. Washington announced Monday that US warplanes had destroyed 283 fuel tankers that were being used to transport oil to help fund the Islamic State group in eastern Syria.