Pictures show bomb disposal teams searching a block of flats in Rooksdown as part of a counter terror operation.
Officers descended on Penny Black Lane in Rooksdown on Thursday, searching a block of flats.
It comes after a 25-year-old Basingstoke man was arrested by counter terror officers.
He was first arrested on suspicion of possessing a firearm without a licence on Wednesday, before being further arrested on suspicion of possessing or making explosives and possessing Class A drugs.
Counter Terrorism Policing South East (CTPSE) is leading the investigation, and the man remains in custody.
Hampshire Police said there is no wider threat to the public.
The road has since reopened.
Chief Inspector Matthew Reeves, District Commander for Basingstoke and Deane, said: “I understand that this is a worrying time in the local community, thankfully incidents of this nature are relatively rare.
“We are assisting our colleagues at Counter Terrorism Policing South East and our partner agencies to address any concerns you may have.
“You may notice an increased police presence, please don’t be alarmed, officers are involved in the investigation and are there to assist and support. Please approach these officers if you have any concerns or questions.
“This is an active investigation so please refrain from speculation, I’d like to take this opportunity to thank the community for their support so far with this investigation.”
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