View of the Chicago skyline taken in 2005 just after sunset. A vast network of high-tech surveillance cameras that allows Chicago police to zoom in on a crime in progress and track suspects across the city is raising privacy concerns.

A vast network of high-tech surveillance cameras that allows Chicago police to zoom in on a crime in progress and track suspects across the city is raising privacy concerns.

Chicago's path to becoming the most-watched US city began in 2003 when police began installing cameras with flashing blue lights at high-crime intersections.

The city has now linked more than 10,000 public and privately owned surveillance cameras in a system dubbed Operation Virtual Shield, according to a report published Tuesday by the American Civil Liberties Union.

At least 1,250 of them are powerful enough to zoom in and read the text of a book.

The sophisticated system is also capable of automatically tracking people and vehicles out of the range of one camera and into another and searching for images of interest like an unattended package or a particular license plate.

"Given Chicago's history of unlawful political surveillance, including the notorious 'Red Squad,' it is critical that appropriate controls be put in place to rein in these powerful and pervasive surveillance cameras now available to law enforcement throughout the City," said Harvey Grossman, legal director of the ACLU of Illinois.

The Chicago police "Red Squad" program from the 1920s through the 1970s spied on and maintained dossiers about thousands of individuals and groups in an effort to find communists and other subversives.

Outgoing mayor Richard Daley has long championed the cameras as crime-fighting tools and said he would like to see one on every street corner.

Chicago police say the cameras have led to 4,500 arrests in the last four years.

But the ACLU said the $60 million spent on the system would be better spent filling the 1,000 vacancies in the Chicago police force.

It urged the city to impose a moratorium on new cameras and implement new policies to prevent the misuse of cameras, such as prohibiting filming of private areas like the inside of a home and limiting the dissemination of recorded images.

"Our city needs to change course, before we awake to find that we cannot walk into a book store or a doctor's office free from the government's watchful eye," the ACLU said.

A police spokeswoman said the department regularly reviews its policies and maintains an "open dialogue" with the ACLU.

"The Chicago Police Department is committed to safeguarding the civil liberties of city residents and visitors alike," Lieutenant Maureen Biggane said in an e-mail.

"Public safety is a responsibility of paramount importance and we are fully committed to protecting the public from crime, and upholding the constitutional rights of all."

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(c) 2011 AFP