Monday's explosions in Boston have led to heightened security elsewhere, with New York, Washington and Los Angeles among the cities taking action within hours of the blasts.
"We're stepping up security at hotels and other prominent locations in the city through deployment of the NYPD's critical response vehicles until more about the explosion is learned," Paul J. Browne, the deputy commissioner of the New York Police Department, .
In Washington, security was increased in the subway and other transportation systems, but there was "no credible threat" against the subway system, Metro spokesman Dan Stessel told Pedestrian traffic on Pennsylvania Avenue in front of the White House was closed about 3:45 p.m. ET, . The Pentagon also added security both inside and outside the building, the television station reported.
Airports in Los Angeles increased security after the blast, the Los Angeles Times , and city police planned to increase security at Los Angeles Dodgers games. Orange County officials also planned to increase security at sporting events, the Times reported.
The Associated Press reported that officials in San Francisco, San Diego, Las Vegas and Atlanta, among other cities, were assessing "potential increases in security measures" in response to the Boston explosions.
The increased security extended overseas. London has a marathon planned for Sunday, and security plans will be reviewed in light of the Boston explosions, a London police spokesman told NBC News.