Nearly three days after the Boston Marathon bombings, authorities are one step closer to understanding who was behind them.

A clear image of a potential suspect has been identified after experts spent the last three days trawling through thousands of images and video tapes of the area where the bombings took place both during the bombings and in the run up to the marathon.

Three explosions went off near the end of the Boston Marathon on Monday, killing 3 people and injuring 183. Among the dead are a 29-year old woman, a Chinese graduate student, and an 8 year old boy.

The bombs were specifically designed to injure as many people as possible, rather than to do any damage to surrounding infrastructure. They took the form of two liquid pressure cookers, packed with pellets, nails and ball bearings. When they detonated, their contents sped through the surrounding area, causing injury to all those they encountered.

Thirteen of the surviving victims have had limbs amputated.

President Obama has stated that the incident was an "act of terror," though he quickly followed up that statement by saying that any attack that specifically targets civilians is an act of terror. The FBI are conducting what they call a "world-wide investigation," yet at this point they still have no idea whether the attack came from an individual or an organisation, or a foreign or domestic group.

No terrorist organisation has accepted responsibility for the attacks, and the Pakistani Taliban have specifically denied responsibility.

A Taliban bombing in Pakistan killed 9 people yesterday. On the same day, 34 people were killed in Pakistan as a result of a major earthquake in neighbouring Iran.