NEW YORK, Aug 7: New York is beefing up security for the World Trade Centre site ahead of the 10th anniversary of the Sept 11, 2001, terror attacks.

The lower Manhattan force will eventually rise to 670 — larger than any of the 76 precincts in the five boroughs — and entire police departments in other cities across the country.

The thousands of people expected to visit the Sept 11 memorial after it opens this fall will endure airport-style screening and be watched by closed-circuit cameras as part of the attack site opens publicly for the first time since 2001.

Securing the World Trade Centre site — which also has a skyscraper rising above the skyline — from terror attacks has been one of law enforcement's most pressing problems long before the Al Qaeda attack that destroyed the towers.

In 1993, Islamic extremists exploded a rented van rigged with fertilizer bomb in a trade centre parking garage, killing six people and injuring more than 1,000 others. And in 2006, authorities alleged a Lebanese man loyal to Osama bin Laden plotted to flood the site and the rest of lower Manhattan by exploding backpacks in commuter train tunnels under the Hudson River.

While some view the resurrection of the 16-acre property as a triumph of the nation's resolve, law enforcement believe terrorists see it as another chance to prove their tenacity.

“Without question it is a target, because it has tremendous symbolism,” said James Kallstrom, a former top FBI official who headed the New York City office in the 1990s. “Going back and attacking a landmark that was already attacked once is the ultimate challenge.”

The site isn't the target of a current known plot, but it “remains squarely in the terrorists' crosshairs,” says Police Commissioner Raymond Kelly.

Fears of a repeated plot against the site years ago resulted in its signature skyscraper being redesigned.

An original plan putting 1 World Trade Centre 25 feet off a state highway near the Hudson River raised concerns by the NYPD that it could be vulnerable to car or truck bombs. A redesign moved it farther off the street and incorporated a windowless 200-foot base.

Developers and law enforcement also have grappled with how to best police the anticipated steady flow of tourists, workers and commerce at the site without turning it into an inhospitable, armed camp.

Kallstrom, while the top counterterrorism adviser to former Gov. Gov. George Pataki in the mid-2000s, was an architect of an ambitious security plan for 1 World Trade Center — scheduled to open in 2013 — the National Sept 11 Memorial & Museum and other office towers and transit at the site.

The measures — combining architectural innovation, high-tech gadgetry and good old-fashioned manpower provided by the NYPD, the Port Authority of New York and New Jersey police and private security firms — will make it “a very, very secure site,” Kallstrom said.

Police plan to use a vehicle security centre to screen tour buses, trucks and cars before they enter the site and park or makes deliveries using an underground roadway. Pedestrian traffic, including visitors to the museum, also will be screened before they can enter the central plaza.

Ticketed visitors to the memorial will be funnelled into a security screening room with airport-style metal detectors and X-ray machines. Employees and frequent visitors will be pre-screened so they can bypass regular checkpoints.

The security plan also calls for 400 closed-circuit surveillance cameras in and around the trade centre site. Live feeds will be monitored around the clock at an NYPD command centre located in a private office building near Wall Street.

A computer system there uses “video analytic” computer software designed to detect potential threats like unattended bags, and retrieve stored images based on descriptions of terror or other criminal suspects.

Final touches are also being put on another ambitious piece of the plan: Screening every car, truck and other vehicle for radioactive materials — evidence of a possible dirty bomb — and other potential threats as they enter lower Manhattan. To achieve that, police are installing cameras, radiation detectors and license-plate readers at the 16 bridges and four tunnels going in and out of Manhattan.

In addition to NY police, Port Authority of New York and New Jersey police officers are also on the site; the agency wouldn't disclose how many for security reasons.—AP