Boston, Apr 16: Two bombs exploded in the packed streets near the finish line of the Boston Marathon on Monday, killing at least three people and injuring more than 130 others in a terrifying scene at the world's oldest and most prestigious marathon, authorities said.
A senior U.S. intelligence official said two other explosive devices were found near the end of the 26.2-mile (42-kilometre) course.
There was no word on the motive or who may have launched the attack, and police said no suspect was in custody.
Authorities in Washington said there was no immediate claim of responsibility.
The twin blasts at the race took place almost simultaneously and about 100 yards (90 metres) apart, knocking spectators and at least one runner off their feet, shattering windows and sending smoke rising over the street.
Some 23-thousand runners took part in the race, which winds up in the heart of central Boston near Copley Square, near the Prudential
Tower and the Boston Public Library.
Boston Police Commissioner Edward Davis asked people to stay indoors or go back to their hotel rooms and avoid crowds as bomb squads methodically checked parcels and bags left along the race route.
He said investigators didn't know whether the bombs were planted in mailboxes or trash cans.
He said authorities had received "no specific intelligence that anything was going to happen" at the race.
The Federal Aviation Administration barred low-flying aircraft from within 3.5 miles (5.6 kilometres) of the site.
A fire broke out at the John F. Kennedy Library a few miles (kilometres) away.
The police commissioner said it may have been caused by an incendiary device but it didn't appear to be related to the bombings.
About four hours into the race and two hours after the men's winner crossed the line, there was a loud explosion on the north side of Boylston Street, just before the photo bridge that marks the finish line. Another explosion could be heard a few seconds later.
By that point, more than 17-thousand of the runners had finished the race, but thousands of others were farther back along the course.
Authorities redirected the runners to safety off the course.
