NEW YORK (CBSNewYork/AP) – A Brooklyn man has been arrested on charges that he tried to help the Islamic State group, in part by encouraging attacks on New York’s subway system.

Zachary Clark was arrested Wednesday.

WEB EXTRA: Read the indictment (.pdf)

Federal authorities say he provided instructions on how to plan attacks on U.S. soil and encouraged Islamic State group supporters to attack well-populated areas.

“As alleged, Zachary Clark twice pledged allegiance to ISIS, and posted on encrypted pro-ISIS chatrooms numerous exhortations and instructions on bomb-making and other terrorist acts to be carried out in New York. Thanks to the Joint Terrorist Task Force, Clark now faces serious criminal charges for his alleged support of a terrorist organization bent on killing Americans,” said U.S. Attorney Geoffrey S. Berman.

“Today’s arrest in Brooklyn is a reminder that New York City remains a top terrorism target in the United States,” said NYPD Commissioner James O’Neill. “The NYPD and all of our law-enforcement partners remain vigilant in this ongoing fight against terror and anyone who would plot to do us harm.”

A defense lawyer declined to comment.

Authorities say the 40-year-old Clark this year pledged allegiance to the Islamic State leader who was killed in October and also his replacement.

Prosecutors say Clark provided instructions on how to attack New York City and posted photos on encrypted pro-ISIS chat rooms. One post included a call to arms against law enforcement and attacks on the New York City subway system.

He allegedly posted a manual on knife attacks, which states “the thought of plunging a sharp object into another person’s flesh” is “never an excuse for abandoning jihad.”

Authorities say there was also a manual on how to build a bomb entitled “Make A Bomb In The Kitchen Of Your Mom.”

He was charged with providing material support to IS and distributing information relating to explosives and weapons of mass destruction.

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)