BOSTON (AP) - BOSTON (AP) - Police say at least three people have been killed in the explosions near the finish line of the Boston Marathon.
The explosions today also injured more than 130 people, knocking spectators and at least one runner off their feet.
Some of the victims lost arms and legs. Other injuries included broken bones, shrapnel wounds and ruptured eardrums.
A senior U.S. intelligence official said two other bombs were found near the end of the 26.2-mile course.
President Barack Obama vowed that those responsible will "feel the full weight of justice."
A White House official speaking on condition of anonymity because the investigation was still unfolding said the attack was being treated as an act of terrorism.
Authorities shed no light on a motive or who may have carried out the attack, and police said they had no suspects in custody. Authorities in Washington said there was no immediate claim of responsibility.