White House labels Boston blasts as 'act of terror'

Over 100 injured, 3 dead in twin explosions near finish line of annual marathon; 3rd explosion reported at city's JFK library; White House treating blasts as 'terror' incident, investigating source of attack.

Boston explosion ambulance 15.4.13 370 (photo credit: Reuters)
Boston explosion ambulance 15.4.13 370
(photo credit: Reuters)
US authorities do not yet know who planned and carried out explosions at the Boston marathon Monday, but they are handling the incident as "an act of terror," a White House official said.

"Any event with multiple explosive devices - as this appears to be - is clearly an act of terror, and will be approached as an act of terror," the official said."However, we don't yet know who carried out this attack, and a thorough investigation will have to determine whether it was planned and carried out by a terrorist group, foreign or domestic," the official said.Two bombs ripped through the crowd at the finish line of the Boston Marathon on Monday, killing at least three people and injuring more than 100others with some victims suffering amputations, the Boston Police Department said.It was the worst bombing on U.S. soil since security was tightened after the attacks of Sept. 11, 2001, and President Barack Obama promised to hunt down whoever was responsible for the attack on a day when tens of thousands of spectators packed the streets to watch the world-famous race.

Two explosions hit the Boston Marathon as runners crossed the finish line on Monday, killing at least two people and wounding dozens on a day when tens of thousands of people pack the streets to watch one of the world's best known marathons.

The FBI had taken lead in investigations through a Joint Terrorist Task as of late Monday, and was in the process of going through property that was discarded at scene.

No one has been arrested and the White House official said it would have to be determined whether the attack came from a foreign or a domestic source.Boston police also reported another explosion at the John F. Kennedy Presidential Library, which is three miles from the marathon's finishing line.

Two explosions hit the Boston Marathon as runners crossed the finish line on Monday, killing at least two people and wounding dozens on a day when tens of thousands of people pack the streets to watch one of the world's best known marathons.

"We are not certain that these incidents are related, but we are treating them as if they are," Boston Police Commissioner Ed Davis told a news conference.Boston police said two people were killed and dozens wounded in the explosions on the marathon scene.

Two explosions hit the Boston Marathon as runners crossed the finish line on Monday, killing at least two people and wounding dozens on a day when tens of thousands of people pack the streets to watch one of the world's best known marathons.

Davis said that the blasts, apparently some 50-100 meters apart, caused "multiple casualties." He added urged people to stay home or go back to their hotels, and to avoid congregating in large crowds. "People should be calm, but they should understand that this is an ongoing event," he said.  

Two high-level US law enforcement officials said one or more bombs were responsible for the explosions."It sounded like a sonic boom. I haven't stopped shaking yet," said Melissa Stanley, who watched her daughter cross the finish line four minutes before the explosions.A fireball rose from behind spectators and a row of flags, video posted on the New York Post website showed. Other pictures showed blood stains on the ground and several people knocked down.Massachusetts General Hospital was treating dozens of  victims of the explosion in its emergency room, six of them in critical condition, a spokeswoman said.

Matt Rand contributed to this report.