At least three people were killed Monday and more than 100 others injured, some critically, after a pair of powerful explosions ripped through a crowd near the finish line while the prestigious Boston Marathon was still in progress, local authorities and media in Boston reported.
US President Barack Obama on Monday evening vowed that those responsible for the blasts would be tracked down and punished, saying they would feel the “full weight of justice.”
“We will get to the bottom of this,” Obama in a short statement delivered at the White House.
Obama did not use the word “terrorism” or “terrorist,” and he said it remained unclear who was responsible for the attack or what their motivations were. He added that he had been in contact with local authorities in Boston as well as the directors of the US Federal Bureau of Investigation (FBI) and the US Department of Homeland Security.
Federal authorities are classifying the bombings as a terrorist attack, though it is unclear whether the origin was domestic or foreign, CNN cited federal law enforcement officials with knowledge of the investigation as saying.
Images emerging from the aftermath of the carnage included blood-spattered asphalt and at least one man with most of his lower left leg missing.
According to the latest reports, more than 140 people were injured, the youngest of them is only two years old. CNN said eight children were wounded. According to the Boston Children`s Hospital, four children aged two, seven, nine and 12 are being treated from various blast-related injuries there.
The Boston Medical Center said at least 16 of its patients are in critical condition.
NBC News reported that one of the three people killed was 8 years old.
A third explosion at the John F. Kennedy Presidential Library in Boston about an hour after the simultaneous blast appeared to be the result of a fire and unrelated to the explosions at the marathon, the Boston Police Department said on its Twitter feed.
The Wall Street Journal said in its online edition that Boston law-enforcers have uncovered five unexploded bombs in the area, among bags left by viewers who were fleeing the scene in panic.
Two more explosive devices were found near the site where two bombs detonated earlier and were being dismantled, The Associated Press cited a senior US intelligence official as saying.
There was no immediate claim of responsibility for the attack, though authorities stepped up security in several US metropolitan areas in the hours following the attack, including in Washington and New York.
Boston Police Commissioner Ed Davis told a news conference that contrary to media reports, no suspects have been detained so far. "We are questioning many people, but there is no suspect in custody,`` he said.
At least one runner fell to the ground and others scattered in various directions as one of the explosions went off shortly before 3 p.m. EDT (1900 GMT), video from local television showed, while crowds of spectators scrambled to get away from the smoke-filled street in central Boston.
The twin blasts came with an interval of 12 seconds. According to police, two explosive devices were planted about 50-100 meters (160-320 feet) from each other.
US television networks broadcast live footage of rescue workers on the scene trying to clear away barricades and decorations that lined the Boston avenue near the finish line of the famed marathon where the explosions occurred.
State police officer Roupen Bastajian told BBC News that he ran toward the epicenter of the blasts and began tending to the wounded, dozens of whom had missing limbs.
“We started grabbing tourniquets and started tying legs,” Bastajian was quoted as saying. “At least 25 to 30 people have at least one leg missing, or an ankle missing, or two legs missing.”
“People started screaming and yelling at each other, trying to find friends and family members,” marathon participant Rachel Sibly, who was about 60 feet (18 meters) from the finish line when the devices exploded, told ABC News.
“People started running away from the finish line. There were sirens filling the streets and heading back to the finish line. It was absolutely terrifying,” Sibly said.
One camera caught one of the explosions on video as it occurred. The footage showed racers running toward the finish line as a sudden blast alongside the street blew decorative flags and barricades into the avenue.
“There was a huge explosion, a loud blast … and then there was smoke rising into the air,” an unnamed eyewitness was shown saying on local television. “At that point everybody started to go crazy.”
Local television showed emergency workers lifting people onto stretchers and evacuating them from the area while police attempted to clear the street and establish order in the busy commercial district of Boston where the explosions occurred.
Monday was a state holiday – Patriots Day – in Massachusetts and the route of the marathon through central Boston was packed with spectators who had turned out for the annual race.
Video footage from helicopters overhead showed one of the city`s main thoroughfares where one of the explosions occurred strewn with debris and cluttered with emergency vehicles.
Updated at 2:58 with statement from US President Barack Obama, information about the injury toll, the reported death of an 8 year old child, and Boston police comments about a third blast.

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