Security tightened up ahead of Obama inauguration in Washington D.C.

Based on the knowledge that the London subway bombers in 2005 used outlying feeder stations as staging points, the agents will move through the crowds on foot looking for suspicious behavior.

Teams of intelligence analysts, evidence response technicians, bomb experts, cyber security specialists, hostage negotiators, emergency medical personnel and SWAT units will also be nearby and out of sight in off-site locations unless they are needed.

Public and private buildings will be closed to normal business near where Obama will be sworn in and along the parade route up Pennsylvania Avenue.

With roads and five major bridges leading into the city closed for the inauguration, and vehicular traffic excluded from large parts of downtown, transit officials have warned riders of "crush conditions" and long waits for buses and subways.

Fighter jets will provide air cover and Coast Guard boats equipped with automatic weapons will patrol the Potomac River.

Chemical, biological and radiological detectors, installed after the 9/11 terror attacks, are already in place.

Businesses and hoteliers have been briefed to be watchful during the inaugural events, in part because the authorities want to increase security awareness after the Mumbai attackers last November singled out soft targets like hotels that were lightly secured.

So far, analysis of intelligence has not yielded evidence of an overseas or domestic threat, according to the Federal Bureau of Investigation.

Editor:Zhang Pengfei