Bin Laden backlash? What US cities are doing to stop terror attacks.

Taking extra care in the wake of Osama bin Laden's killing Sunday, law-enforcement agencies in major cities nationwide are sending out extra officers to patrol potential terrorist targets including schools, public transportation networks, and sporting events.

While officials say there have been no specific threats against American targets since Sunday – and any complex attack would take time to plan – a more immediate threat could come from homegrown sympathizers.

Among the measures being taken:

• Boston and Massachusetts law-enforcement agencies are providing more noticeable patrols as a precautionary measure. "To reassure the riding public, we are going to increase our high-visibility patrols on the trains, probably at least through the end of the week,'' said Boston Transit Police Chief Paul MacMillan in a security briefing. This includes more security inspections in stations and on train cars, as well as the use of explosive-detection dogs.

"Everyone is on appropriate, heightened alert with greater presence at the airport and on the T [Boston mass-transit system], but not because we have any new or concerning information – just in an excess of caution,'' said Gov. Deval Patrick at a security briefing.

• Miami-Dade County has responded with Operation Viper, with agents from local and federal agencies monitoring the mass-transit system for suspicious activity. Police officers with canine teams will be at Miami International Airport, which will also conduct more bag checks and random inspections at security gates, said Maria Levrant, an airport spokeswoman.

• Chicago will have more officers on the street indefinitely starting Tuesday. The Chicago Police Department is increasing foot patrols, as well as camera and car surveillance. In addition, new metal detectors will be used at Chicago Bulls basketball games at the United Center.

• Los Angeles Police Department Chief Charlie Beck said at a press briefing Monday that the city would step up security at Dodgers and Lakers games. He also asked residents to pass along tips on possible threats by reporting any suspicious behavior. "This can be many things, chemicals … increased traffic … anything that you can see that are out of place," he said. "If they look out of place to you, there probably is a reason.”

Since the invasion of Iraq in 2003, the Los Angeles County Sheriff’s Department and the LAPD have coordinated in refining a playbook of logistical responses to potential attacks. "If you will, the head of the snake has been cut off, so everything right now is euphoric, people are grateful, but it’s also important to be vigilant as we move forward,” says Steve Whitmore, spokesman for Sheriff Lee Baca. “Obviously people are concerned about retaliation."

LAPD Assistant Police Chief Michel Moore told NPR that law enforcement would be keeping even closer tabs than usual on religious institutions, the port of L.A., the airport, and the financial district downtown.

“These are all areas that we know from our history are always viewed by Al Qaeda and others as potential targets,” says Mr. Moore.

• Wire material was used in this report.