Four suspected pipe bomb type devices and working parts of a firearm were recovered during a search operation in the People's Park area of Portadown, the PSNI said on Tuesday.
The pipe bombs were not viable.
"The investigation is at an early stage and we are working to establish how old the items are and whether this find is linked to historic terrorist activity," PSNI Insp Leslie Badger said.
Ulster Unionist MLA and Upper Bann Westminster candidate Doug Beattie welcomed the discovery and said the weapons appeared to be "old Troubles-related munitions".
“This has been a productive search in which the PSNI have been assisted by military colleagues to continue to keep the entire community safe and recover any weapons, whether old or new, and place them where they can no longer cause harm,” he said.
