A former US schoolteacher who became a high-ranking Islamic State official and organized an all-female IS military battalion, pleaded guilty Tuesday to supporting a foreign terrorist group, the Justice department said.

Allison Fluke-Ekren, 42, admitted to engaging in "terrorism-related activities" in Syria, Libya, and Iraq between 2011 and 2019, the department said in a statement.

"Fluke-Ekren ultimately served as the leader and organizer of an ISIS military battalion, known as the Khatiba Nusaybah, where she trained women on the use of automatic firing AK-47 assault rifles, grenades, and suicide belts," the department said.

"Over 100 women and young girls, including as young as 10 or 11-years-old, received military training from Fluke-Ekren in Syria on behalf of ISIS," they said, referring to the Islamic State.

The department said that she had lived in Egypt and then Libya with her late husband, who was a member of the extremist Ansar al-Sharia group.

The two took documents from the US diplomatic mission in Benghazi after it was attacked in 2012 and summarized them for Ansar al-Sharia, it said.

After that they went to Turkey and Syria, where her husband became a leader of an Islamic State sniper group.

While in Syria, the department said, she spoke of desires to bomb a shopping mall or a university campus in the United States.

In 2016-17 she became leader of the all-woman Khatiba Nusaybah battalion, which undertook physical, medical and weapons training to support Islamic state.

Fluke-Ekren was apprehended in Syria sometime after the early-2019 territorial defeat of the extremist group by US-led coalition forces.

She was flown to the United States on January 28 from an undisclosed location and charged with supporting a foreign terrorist organization, a charge which brings up to 20 years in prison.

She never went on trial, however. The court record indicates that her attorneys and the Justice Department spent the past months negotiating her guilty plea on a single count.

She will be sentenced on October 25.