It has been reported that two explosions have gone off at the end of the Boston Marathon, with several runners believed to be injured. The blasts occurred a few seconds apart, leaving Boston's Copley Square in smoke.
The explosions are said to have occurred as some of the final runners finished the marathon. Video and twitter images show emergency services present at the scene, with injured spectators taken to a medical tent.
A spokeswoman for the Boston Police Department commented: "There was an explosion, police, fire and EMS are on the scene. We have no indication of how many people are injured."