A New York man has been detained without bail and faces terrorism charges after he became a sniper and weapons trainer for the "Islamic State" (IS) group, according to court documents unsealed on Friday.

Ruslan Maratovich Asainov, a 42-year-old naturalized US citizen from Kazakhstan, was detained by the Syrian Democratic Forces and transferred to FBI custody earlier this week, prosecutors said. He was charged with providing material support to IS, including providing training to terrorist soldiers and attempting to recruit members.

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Defense attorney Susan Kellman said outside of a Brooklyn courthouse that her client was "very pleasant, very forthcoming" but was reluctant to speak when the judge asked him if he understood his rights.

"He answers to a higher authority," the lawyer said. "He says his ruler is Allah."

'Worst terrorist organization in the world'

A resident of the New York borough of Brooklyn from 1998 to 2013, Asainov traveled to Turkey in December 2013 before heading to Syria, federal prosecutors said.

There he joined IS and rose through the ranks as a sniper, becoming an "emir" in charge of training other members in the use of weapons.

Read more: Germany brings home 'Islamic State' children from Iraq

He stayed in contact with some people in the United States, sending messages and photographs of himself in action.

"We are the worst terrorist organization in the world that has ever existed," one of his messages from 2015 said, according to court documents.

He tried to recruit a person in the US to go to Syria and join the militant group, saying he'd help the person get a job, food and $50 (€44.51) per month. He also asked a confidential informant to send him $2,800 so he could buy a scope for his rifle.

Experts estimate that approximately 40,000 foreign fighters from 80 countries may have joined the militant group in Iraq and Syria between 2013 and 2018. The fate of IS prisoners captured in Syria has become a controversial issue.

dv/cmk (AFP, AP, dpa, Reuters)

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