Los Angeles police Lt. Andrew Neiman said the department was urging officers to be extra vigilant around large crowds and would increase security at sporting events such as the Los Angeles Dodgers game Monday night.
The department was also activating its emergency operations center to increase communication and increasing patrols for transit and other critical areas, Los Angeles County Sheriff's spokesman Steve Whitmore said.
Police in Washington, San Diego, Vegas and Atlanta were monitoring events closely and assessing potential increases in security measures. Agencies were also stepping up social media response, telling the public via Twitter and Facebook to report suspicious activity to the police.
Police at three major Los Angeles area airports, including Los Angeles International Airport, were in a "heightened state of vigilance," with increased patrols to make it visible that more police were on duty Monday, said Chief of Airport Police Patrick Gannon.
"We have no indications that suggest there's a nexus from Boston to the Los Angeles airport, but in an overabundance of caution, we have heightened our patrols," Gannon said.
British police also said they were reviewing security plans for Sunday's London Marathon. It's the next major international marathon. A London Metropolitan Police spokesman said police are working with marathon officials to review security plans with an eye toward establishing a larger security presence.
Officials in San Francisco, Los Angeles, Orange County, San Diego and Sacramento were reviewing information from federal authorities for possible threats, said Kelly Huston, assistant secretary of the California Emergency Management System.
Copyright 2013 The Associated Press.