Bahrain Mirror (Reuters): The United States blacklisted three people on Thursday for working for Islamic State, including the militant group's most prominent ideologue and a senior oil official.

Turki al-Bin'ali was sanctioned for helping Islamic State recruit foreign fighters, the U.S. Treasury said in a statement.

Bin'ali, 31, was an early supporter of Islamic State and authored a frequently cited biography of the group's leader, Abu Bakr al-Baghdadi.

Experts said the preacher's writings helped lay the religious legal groundwork for Islamic State to declare a "caliphate," which it did in 2014 in parts of Syria and Iraq it controls.

Bin'ali is believed to be the group's chief religious authority, and has written a text that traces Baghdadi's lineage to the Prophet Mohammad, said Cole Bunzel, an Islamic State expert at Princeton University.

Bin'ali issued a treatise that rallied militant Islamists to the cause and has denounced Islamic State's many Muslim critics. Bahrain revoked Bin'ali's citizenship in 2015.

Sanctions are unlikely to have any impact on Bin'ali, who comes from a wealthy Bahraini family, Bunzel said.

"He's the most ideologically committed person to this movement that I know," he said. "To him, this is very much not about money."

A Treasury spokeswoman said Thursday's actions were the first U.S. sanctions to target Bin'ali. The sanctions freeze any U.S. assets the men might have and prohibit Americans from dealing with them.

While they have little immediate practical impact, the sanctions have a "naming and shaming" effect and allow for follow-on actions against people connected to Bin'ali, said Matt Levitt, a former U.S. Treasury official now at the Washington Institute for Near East Policy.

Another man sanctioned on Thursday was Faysal Ahmad Ali al-Zahrani, from Saudi Arabia, who the Treasury Department said is responsible for Islamic State's oil and gas activities in areas of northeastern Syria.

Treasury said Zahrani for a time answered directly and transferred funds to top Islamic State financial official Abu Sayyaf, who was killed in a U.S. Special Operations Forces raid last May.

A U.S. Treasury official said this week that U.S.-led coalition air strikes targeting Islamic State's oil and cash storage sites, have helped force the group to cut its fighters' pay by up to 50 percent.

Husayn Juaythini, born in a refugee camp in Gaza, was also sanctioned and was trying to establish a foothold for Islamic State in Gaza, the Treasury said.