bostonAP Photo/Charles Krupa

Police officials have confirmed that one of the fatalities at the Boston Marathon bombing was an eight-year-old boy.

At least three people have been killed and over 140 injured –  including up to 10 with amputated limbs – after explosions at the finish line of the Boston Marathon, say Boston Police.

The atmosphere of the event, in aid of charity, was destroyed and confused after the two blasts.

Victims covered in blood were rushed to an insufficient medical tent originally set up for tired runners.

The scene was almost immediately locked down, whilst the Emergency services began to arrive.

According to reports, witnesses inside the Fairmount Copley Plaza Hotel, heard booms that were said to resemble the sound of thunder, near the finish line.

The cause of the explosions has yet to be confirmed.

Video by Steve Silva

“There are a lot of people down,” said one runner, quoted by AP news agency.

President Barack Obama had been informed about the disaster in Boston, while Vice President Joe Biden said: “Our prayers are with those people in Boston who have suffered injury.”

The Associated Press news agency said a loud explosion was heard on the north side of Boylston Street, just before the bridge that marks the finish line. Another loud explosion happened a few seconds later, and smoke covered the blasts.

Mike Mitchell, a Canadian runner who had finished the race, said he was looking back at the finish line when he saw a “massive explosion.”

Smoke rose 50ft (15m) in the air, he told Reuters news agency, and people began running away and screaming after hearing the noise. “Everybody freaked out,” he said.

Amber Davies, a student from De Montfort, Leicester, has said of the incident: ‘It is a tragedy that disasters like this are happening around the world, especially when the people harmed were those trying to do good in the world.’

Runners heading for the end of the marathon were detoured away from the smokey scene that remained on lock down.

The Boston Marathon is a yearly event that attracts a large volume of runners and tens of thousands of spectators.

Meanwhile, authorities in New York have told the Reuters news agency they have deployed anti-terrorism units at key sites, including prominent hotels.