Camera shy? New York may not be the city for you.

With the Police Department reportedly considering a plan to blanket parts of Manhattan with closed-circuit surveillance cameras and the Metropolitan Transportation Authority working to double the number of cameras in the subway system, Mayor Bloomberg said in his State of the City address yesterday that he would seek to install cameras that automatically swivel at the sound of a gunshot.

The Wall Street Journal on Wednesday reported that the Police Department is looking into constructing a network of cameras similar to the “ring of steel” that surrounds the City of London, the British capital’s financial district, and one of its historic centers.

Implemented in 1993 after several terrorist attacks by the Irish Republican Army, the “ring of steel” monitors all comings and goings into the neighborhood, which has its own police force. About 20 roads that lead into and out of the area have been narrowed, and cameras record the license plate numbers of all cars entering the neighborhood. In an emergency, some roads can be closed to block vehicles from entering and exiting while cameras search the streets.

The Journal said the Police Department’s focus is on Lower Manhattan, a neighborhood that resembles the City of London in size, population, and target density. It also reported that “a law enforcement official close to the situation” said the Police Department’s plans may extend to Midtown as well.

A spokeswoman for the mayor’s office referred a reporter to the Police Department, which did not return requests for information or comment.

Though unfamiliar with the specifics of the project, which is still in the planning stage, local lawmakers said they approve of the sentiment behind the proposal.

City Council Member Peter Vallone Jr., a Democrat of Queens, said in a telephone interview that camera surveillance is “the future not just in New York City, but in the entire country.”

The council in 2004 voted overwhelmingly to pass a bill Mr. Vallone introduced that required all public schools to install security cameras. He lauded the surveillance as a successful deterrent to graffiti and other crimes. “If people know there’s a camera there, they won’t commit a crime,” he said.

Assemblyman Vincent Ignizio, a Republican of Staten Island, told The New York Sun that the program would be a “supplement to the great work the NYPD does to stop crime and thwart terrorist attacks.” Mr. Ignizio, the chairman of the Assembly Republican Review Committee, said he could not speak for his colleagues, but that the “Assembly minority conference is certainly in favor of that which protects New York City.”

The Police Department does not need legislative approval to install the cameras, though the Legislature can require it to do so. A terrorism expert with more than 40 years’ experience in military and private counter-terrorism work, Thomas Preston, said in a telephone interview that camera surveillance is an effective deterrent to terrorism but is effective only if manned by a trained, vigilant, and not overworked staff.

Members of the ACLU and civil liberties advocates have criticized the plan and other public surveillance programs as an infringement of privacy and freedom. Supporters of public cameras disagreed.

“If you’re out in public, you have already exposed yourself anyway,” Mr. Preston said.

Other camera surveillance programs are in the works.

In his State of the City address, the mayor said the city in the coming year “will pilot new technology that uses microphones to instantly direct video cameras to the source of gunshots, ensuring that shooters are seen as well as heard.”

The Metropolitan Transit Authority announced in August 2005 a three-year plan to add 1,000 closed-circuit cameras and 3,000 motion sensors to the subway’s security system. There are already 1,000 cameras in the subway.