Boston Bombings.

An eight-year-old boy waiting at the finish line to give his father a hug was among three people killed and more than 144 injured when two explosions rocked the Boston Marathon in what can be described as the worst terrorist atrocity since 9/11.

Martin Richard died after bombs hidden in rubbish bins were detonated within seconds of each other during the Patriots’ Day bank holiday yesterday, sending terrified runners and spectators fleeing for their lives and leaving a scene of 'unspeakable horror'.

Boston police closed off the city as a ‘danger zone’ as witnesses described seeing body parts flying through the air and shoes that 'still had flesh in them' in an attack that has sent shockwaves across the world.

At least 17 of the injured are in a critical condition and it is thought as many as 30 victims may have needed amputations or major corrective surgery on maimed limbs.

At least eight of the wounded are thought to be children, including a two-year-old boy who suffered a head injury.

Today, as the United States remained on full alert, President Barack Obama vowed to hunt down the culprits and 'hold them accountable'.

No-one has yet claimed responsibility for the bombings and there is no suspect in the custody, but it is being reported that a Saudi Arabian national is being kept under police guard in an undisclosed Boston hospital.

In London, Scotland Yard confirmed security arrangements were being reviewed ahead of Baroness Thatcher’s funeral tomorrow and Sunday’s marathon.

Video footage showed an explosion going off in the heart of the crowd that had lined the streets of the Massachusetts city yesterday to watch the famous sporting event.

After the blasts, two more suspicious devices were found in the city’s Mandarin Oriental and Lenox hotels. Both were evacuated and the suspected bombs dismantled.

See video footage of the blast below: