The boy, who cannot be named for legal reasons, was charged on Wednesday with the preparation of terrorist acts in violation of Article 5 (1) (a) of the Terrorism Act 2006 linked to Islamist terrorism.
He was arrested on Friday by Hampshire gendarmerie officers and later detained under section 41 of the Terrorism Act by CTPSE detectives.
A CTPSE statement said, “We know the Eastleigh community may be concerned about this news, but the Hampshire police have been working closely with colleagues from Counter Terrorism Policing South East on this investigation and we want to reassure you that we think the survey is isolated and without known risk to the community.
“If you think you have seen something suspicious that may be related to terrorist activity, have the confidence to share these concerns.
“It can be unusual behavior in a particular place or at a particular time of day – don’t count on others. “