A New York judge sentenced an American man to life in prison Tuesday for his role as a sniper for the Islamic State (IS) group.

Brooklyn federal court judge Nicholas Garaufis also handed down three other sentences — totaling another 100 years — to Ruslan Maratovich Asainov for providing material support to the jihadist group resulting in death, conspiracy to provide material support, and obstruction of justice.

Asainov, 46, continued to maintain his support for IS — which the United States has designated a "foreign terrorist group" — throughout his trial.

"Today's sentence rightly holds Asainov responsible for the carnage he inflicted as a sworn member of ISIS and protects the world community from this avowed killer," federal prosecutor Breon Peace said, using another acronym for the IS group.

"The defendant committed his life to that terrorist organization and became a lethal sniper for ISIS in Syria, training many other ISIS members to shoot to kill as ISIS waged its brutal, barbaric campaign," Peace added.

"To this day, the defendant maintains his unrepentant allegiance to that hateful cause."

Asainov, who is originally from Kazakhstan, left his family in New York in 2013 to travel to Syria, where he joined the ranks of IS fighters until his capture by the Syrian Democratic Forces (SDF) in 2019.

During his time with IS, Asainov rose through the group to become one of its so-called emirs, training other fighters in weapons and helping to build training camps.

He stayed in touch with US contacts even while he was in Syria, sending messages and photos of himself on the battlefield.

"We are the worst terrorist organization in the world that has ever existed," Asainov wrote in one such 2015 message, according to court documents.

He left for Syria with fellow American Mirsad Kandic, who was born in Kosovo and was himself sentenced to life in prison in the United States in July.