Three people were killed and more than hundred others were injured as two powerful bombs exploded near the finish line of the Boston Marathon on Monday.

Three people were killed and more than hundred others were injured as two powerful bombs exploded near the finish line of the Boston Marathon on Monday.

The dead included an 8-year-old boy, news agencies reported, adding that among the injured, 17 people were reported in critical condition.

"There were so many people in that area that they couldn't get ambulances in there," said Joe Difazio, who was working on communications near the site when the blasts occurred.

Almost three-quarters of the 23,000 runners who participated in the race had already crossed the finish line when a bomb that had apparently been placed in a garbage can exploded. Thirteen seconds later, another bomb exploded several hundred feet away.

Pandemonium erupted as panicked runners and spectators scattered, and rescue workers rushed in to care for the dozens of maimed and injured. The F.B.I. took the lead role in the investigation on Monday night, and Richard DesLauriers, the special agent in charge of the bureau’s Boston office, described the inquiry at a news conference as “a criminal investigation that is a potential terrorist investigation.”

President Obama, speaking at the White House, vowed to bring those responsible for the blasts to justice.
“We will get to the bottom of this,” Obama said.

“We will find who did this, and we will find out why they did this. Any responsible individuals, any responsible groups will feel the full weight of justice.”

He did not refer to the attacks as an act of terrorism, and he cautioned people from “jumping to conclusions” based on incomplete information.