LOS ANGELES (AP) Police in Los Angeles, New York City, London and other cities worldwide stepped up security Monday following explosions at the Boston Marathon.
President Barack Obama, responding to the explosions at the Boston Marathon, says the United States does not know "who did this or why" but vowed that whoever is responsible "will feel the full weight of justice."
He said: "We will find out who did this and we will hold them accountable."
Obama made his remarks Monday evening from the White House about three hours after two explosions detonated near the marathon's finish line. At least two people were killed and 50 injured in the blasts.
Obama has been in touch with federal law enforcement and Massachusetts officials in the aftermath of the explosions.
The Secret Service reacted cautiously to the blasts, expanding the security perimeter around the White House.
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.
Chief NYPD spokesman Paul Browne said Monday 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.
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.
On Monday, California emergency management officials activated their statewide threat assessment system, which was established following the Sept. 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.
Copyright 2013 The Associated Press
GREGORY KATZ, Associated Press
LONDON (AP) British police are reviewing security plans for Sunday's London Marathon, the next major international marathon, because of the bombs that killed two people at the race in Boston. But there is no known specific or credible threat against the British race at the moment, a security official said.
The London Marathon is a hugely popular race. Last year, some 37,500 athletes competed, with many more watching the springtime event.
London has long been considered a top target for international terrorists, with the government saying the threat level is "substantial." In 2005, a series of suicide attacks on the public transport system in the British capital killed 52 people.
London and mainland Britain also face a moderate threat from Northern Ireland-related terrorism, according to the government.
Two bombs exploded near the finish of the Boston Marathon on Monday, killing two people, and injuring at least 22 others, race organizers and police said.
The situation sparked alarm bells in Britain, where a massive security operation was put in place last summer to protect the successful London Olympics.
Chief Superintendent Julia Pendry, police commander for the London race, said Monday that "a security plan is in place for the London Marathon. We will be reviewing security arrangements in partnership with (the) London Marathon."
A police spokesman who spoke on condition of anonymity because he was not authorized to go on the record said the security presence may be increased.
A security official, who also spoke on condition of anonymity because he was not authorized to speak publicly about the matter, said there are no credible or specific threats against the London Marathon.
The London race's chief executive, Nick Bitel, said marathon officials contacted the police to discuss security plans "as soon as we heard the news" about Boston. He expressed shock and sadness about the situation in Boston, saying "it is a very sad day for athletics and for our friends in marathon running."
AP Writers Paisley Dodds and Cassandra Vinograd contributed to this report.
Copyright 2013 The Associated Press