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New York • New York City Mayor Michael Bloomberg says the police department has secret air and other defenses designed to thwart a terror attack.

The mayor's comments came Monday, a day after police Commissioner Raymond Kelly told "60 Minutes" the NYPD could blow a threatening plane out of the sky. He refused to elaborate, except to say the department would take action only under extreme circumstances.

Bloomberg said that since the Sept. 11 terror attacks, the NYPD has developed counterterror defenses the public may never know about.

It was previously known that the NYPD has helicopters capable of carrying heavy guns that could down small private aircraft.

A North American Aerospace Defense Command spokesman said Monday that it remains responsible for combating major air threats like those in the 9/11 attacks.