A "high-tech listening device" was found in an allotment attached to a housing estate in Londonderry on Monday night, it has been claimed.
Dissident republican party Saoradh said children were playing near the allotment when residents noticed a man wearing dark clothing and a baseball cap bending down as if to tie his shoelace.
The group said he then made his way from the allotment onto a back road and into a dark-coloured car.
Upon searching the area "republican activists" came upon an item that appeared to be a brown stone.
Pictures of the item, however, show it was made of plastic and had an electronic device embedded in it.
Saoradh's Paddy Gallagher claimed: "These images taken by republican activists show in detail the clandestine British device which was deliberately constructed and planted by British Military Intelligence with the sole purpose of eavesdropping and recording potentially months of audio/sound.
"They then collect the device to charge and extract the collated data and return it to a spot of their choice."
Saoradh has been widely reported to be the political wing of the New IRA, one of the largest dissident republican paramilitary organisations, a claim it denies.
The group faced a backlash after journalist Lyra McKee was shot dead by a New IRA gunman while observing rioting in the Creggan area of Derry in 2019.
Saoradh has the support of New IRA prisoners in Maghaberry and Portlaoise Prisons.
High-profile republicans including Colin Duffy have been linked to the party.