The move by the New York Police Department against one of the city’s biggest tabloids was unusual: It issued a subpoena demanding information about a New York Post reporter’s Twitter account and cited an antiterror law passed after the Sept. 11, 2001, attacks.

The legal maneuver has raised concerns that the department, the nation’s largest police force, is taking aggressive steps to control the media’s coverage of the agency.

The subpoena was issued Dec. 9, just days after Dermot F. Shea became police commissioner.

Before his promotion, Commissioner Shea was the head of the department’s detective bureau, where he had gained a reputation for being reluctant to release information to reporters.

The subpoena sought internet service provider addresses, emails and other information affiliated with the Twitter account of Tina Moore, the chief police reporter for The Post.