Richard Barrett, the former United Nations co-ordinator for the al Qaeda and Taliban monitoring team, said the timing of the attack on Patriots’ Day and the relatively small size of the devices suggested the work of a domestic extremist.
But Mr Barrett, who has served with MI5, MI6 and the Foreign Office, said: ‘This happened on Patriots’ Day, it is also the day Americans are supposed to have their taxes in, and Boston is quite a symbolic city. These are all little indicators.’
He added that it was still too early to confidently say who was to blame.
His comments came after U.S. supercop Bill Bratton, a former head of Boston police who is now based in London, warned there are ‘no shortage of potential suspects’ behind the explosions.
Counter terrorism expert Rick Nelson, of the Center for Strategic & International Studies, said the number of co-ordinated blasts suggested a ‘complexity’ that would be difficult for an individual to carry out alone.
‘It was perhaps not one person but a group who were involved,’ he said. ‘The location suggests they were looking for maximum media value so that the explosions were caught by television cameras.’
The two blasts on Monday went off almost concurrently near the finish line of the marathon.
Police initially said a third blast occurred at the John F.Kennedy Presidential Library but later reported it as an unrelated fire.
Cell phone service was shut down across the area to prevent any potential remote detonations as police feared there were secondary devices.