Washington (CNN) The US-backed Syrian Democratic Forces have captured an individual the US assesses to be Mohammed Haydar Zammar, a Syrian-born German national linked to the 9/11 terrorist attacks.

"We can confirm that Mohammad Haydar Zammar, a Syrian-born German national, was captured more than a month ago by SDF partners as part of their ongoing operations to defeat ISIS inside Syria," Pentagon spokesman Eric Pahon told CNN.

Pahon said Zammar "was captured during a unilateral operation conducted by the Syrian Democratic Forces."

"We are working with our SDF partners to obtain additional details," he added, calling Zammar's capture "a strong reminder of the threat posed by ISIS and its network of foreign terrorist fighters."

The spokesman for the People's Protection Unit (YPG), Nouri Mahmoud, and the spokesman for the Syrian Democratic Forces, Mostafa Bari, refused to comment when contacted by CNN.

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