Surgeon Dr Peter Fagenholz describes Boston Marathon injuries

An investigation is under way after two explosions near the finishing line of the Boston Marathon left three people dead and at least 140 injured.

Some of the injured were taken to Massachusetts General Hospital, where Dr Peter Fagenholz told reporters that some people suffered shrapnel wounds and amputations and will require repeat operations in the coming days.

The FBI has taken over co-ordination of what it described as a "potential terrorist inquiry".