Security beefed up worldwide after Boston Marathon blasts

Police in Los Angeles, New York City, London and other cities worldwide stepped up security today following twin explosions at the Boston Marathon that left at least two dead.

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 baseball game tonight.

The department was also activating its emergency operations centre 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, Las 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.

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.

Chief New York Police Department spokesman Paul Browne said that critical response teams were deployed around the city, and officials were stepping up security at hotels and other prominent locations.

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.

California emergency management officials activated their statewide threat assessment system, which was established following the September 11, 2001 World Trade Center bombings.

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.

In Tennessee, the Nashville Predators will host the Vancouver Canucks on Monday night and hockey fans will see "more visible presence around the building," team spokesman Kevin Wilson said.