Officials across the country are boosting security measures following the deadly bombs that rocked the Boston Marathon.
Police in some major U.S. cities, including New York and Washington, are monitoring government buildings, landmarks, transit hubs and sporting events.
New York City Police Commissioner Raymond Kelly says officers have increased security patrols of "iconic" potential targets such as the Empire State Building and Rockefeller Center, locations that are flooded with tourists year-round.
New York City Mayor Michael Bloomberg encouraged New Yorkers to go about their normal routines as they continue to remember those effected by the tragedy in Boston.
In Washington, the U.S. Capitol Police says staff and visitors to the Capitol Complex should expect an increased police presence in and around public areas, including visitor lines at doors and more frequent canine inspections.
Organizers of the the annual George Washington Parkway Classic 16-kilometer and five-kilometer races later this week near Washington say they are making additional security enhancements. They say U.S. Park Police and local authorities are working to provide runners with an outline of the new security measure by Thursday.
Law enforcement agencies have urged the public to report any suspicious activity to the police.