Story highlights ISIS has repeatedly used low-grade chemical weapons, primarily sulfur mustard, in Syria and Iraq

Military officials have downplayed the effectiveness of ISIS' chemical weapons

(CNN) The US announced sanctions Monday on two ISIS chemical weapons experts, the first such effort aimed specifically at the terrorist group's chemical weapons leadership.

ISIS has repeatedly used low-grade chemical weapons, primarily sulfur mustard, in Syria and Iraq.

The new sanctions, which would bar access to any property or interests under US jurisdiction, target Attallah Salman 'Abd Kafi al-Jaburi and Marwan Ibrahim Hussayn Tah al-Azawi, two ISIS leaders involved in the development of chemical weapons, according to the State and Treasury departments.

Al-Jaburi was a senior ISIS leader who oversaw some of the terror group's improvised explosive device factories while also being involved in the development of chemical weapons in Iraq, according to a Treasury Department statement accompanying the announcement.

A member of al Qaeda since 2003, al-Jaburi received chemical weapons training in Syria before returning to Iraq in 2015, the statement said.

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