Two large explosions have been reported near the finish line of the 2013 Boston Marathon 2013 on Monday afternoon.

Witnesses and media sources are reporting that two loud bangs were heard near the finish line by the Fairmount Copley Plaza Hotel, and video footage can be seen at the moment of the first bang near the finish line.

The two bangs were heard about 15 to 20 seconds apart, with some reports describing a ball of flames coming out from the Marathon Sports store near the finish line. It is believed that venue was being used as a press center for the marathon.

Other early reports are claiming at least six people have been injured, although no news has been offered as to their condition. Some reports have reported that some bloodied victims were taken to a medical tent for treatment, and at least six have been taken to hospital. Further injuries are expected to be announced as the situation becomes clearer.

Early video footage has shown chaotic scenes at the location, with some people blown off their feet when the explosion took place, and massive amounts of smoke seen filling the streets where the explosions took place.

The cause of the explosions has not been determined, but some serious destruction has been reported to some temporary structures at the marathon.

Huge amounts of smoke could be seen coming from the Marathon Sports store and marathon officials were seen pulling at some metal railings that were twisted and piled on the ground, seemingly to free some people under them.

Police are being deployed to major landmarks in other large cities across the United States, including New York City, as fears of a possible terrorist attack emerge. However, there has been no confirmation of the cause of the explosions at this time.