Hundreds of anti-Brexit activists erected six mock border posts between Ireland and Northern Ireland on Saturday to highlight their claim that Northern Irish voters face leaving the European Union against their will.
The Border Communities Against Brexit group said it staged the protest to urge the British government to respect Northern Ireland's majority vote for remaining in the EU in a referendum on June 23.
Fifty-six per cent of voters Northern Ireland chose to remain in the EU, compared with 48 per cent across the United Kingdom.
The group said Brexit could damage the economy on both sides through the setting up a "hard border" with customs checkpoints and the closure of some cross-border roads between EU member Ireland and a non-EU Northern Ireland.
It claims to represent "people from all sectors – business, community, farming - as well as individuals who have come together out of concern that the North's remain vote will not be respected."
"We are really worried about the devastating impact that Brexit will have in this region and we want to make sure our voices are heard when decisions are being taken in Dublin, London and Brussels," it said.
A current "common travel area" agreement allows Irish and British citizens to travel between the two countries without a passport and grants mutual voting rights in the two countries.
Many politicians have raised concerns that Brexit could jeopardize the agreement.
On Tuesday, Northern Ireland's High Court opened a hearing of a legal challenge to the British government's right to begin Brexitnegotiations without votes in the national parliament and the regional assembly.