Demonstrators in Belfast on Wednesday backed a call by Irish nationalist party Sinn Fein against a hard Irish border after Brexit, a key point in Britain's divorce talks with the EU.
Braving heavy rain, the roughly 100 protesters carried placards demanding that there be "no border" between the British province and its southern neighbour the Republic of Ireland, which will remain in the bloc.
"The north voted to remain within the EU and that mandate must be respected and acted upon," said John Finucane, a member of Sinn Fein, which organised the protest.
Demonstrators unveiled a poster calling for the province to receive "special status" and urging Irish Prime Minister Leo Varadkar to use his veto to prevent Brussels from moving to the next phase of negotiations with London unless his demands for no post-Brexit border were met.
"If you put a hard border, there will be guns again, even if it takes 10 years," said an anonymous protester, referring to Northern Ireland's dark days of sectarian bloodshed.
An agreement on the border seemed imminent Monday, with Britain promising no difference in regulations between the Irish Republic and Northern Ireland after Brexit in order to avoid the reintroduction of a physical border to check goods.
The border disappeared after the signing of the 1998 Good Friday peace accord, which ended decades of bloody clashes between nationalists who want a united Ireland and Northern Ireland unionists loyal to Britain.
But Arlene Foster, leader of the Democratic Unionist Party that props up Britain's Conservative government, rejected the plan, saying "we will not accept any form of regulatory divergence which separates Northern Ireland economically or politically from the rest of the United Kingdom."
"The DUP position is ridiculous, outrageous," said 41-year-old protester Louise McManus, a health worker.
"The DUP defends more the union with Great Britain than people's livelihoods".
The event was the first of a series of rallies that Sinn Fein plans to hold in Northern Ireland.
Theresa May insisted Wednesday that negotiations on the exit agreement were still progressing.