Riot police officers quickly detained the man around lunchtime after an object was thrown as Britain First’s Jayda Fransen vowed to organise future protests against new mosques being built in Northern Ireland.
The Britain First rally was timed to coincide with a republican parade marking the anniversary of British internment without trial in Belfast, but those demonstrators were barred from the city centre.
Organiser Dee Fennell said: “The only people that are denied entrance to Belfast city centre are the republican people of Belfast, of Derry, of right across this country and beyond.”
The arrested man at the Britain First protest was kept apart from a group of far-right loyalists who attempted to attack him in Donegall Square East.
Riot squad officers from the Police Service of Northern Ireland also separated around 50 Britain First supporters from a smaller band of left-wing anti-Nazi demonstrators in the street from the Belfast Says No to Fascism group.
Gerry Carroll of the left-wing People Before Profit party said they had come to protest against the “poisonous” politics of Britain First.
“We have enough divisions in Northern Ireland without these fascists getting a foothold here in this society. They are only here to ramp up these divisions even further,” Carroll said.
Independent Unionist Jolen Bunting, who shared a platform with Britain First speakers at Belfast City Hall, was asked if she believed the far-right group was racist. She replied: “No!”
Among those to speak was Britain First’s leader, Paul Goulding, who described the empty flag pole where the union flag used to fly over Belfast City Hall as a “symbol of oppression” and claimed that there is “worse to come” for British unionists and loyalists.
Goulding predicted “civil war on British streets” over immigration and Islam.
His supporters heckled a correspondent from the Irish Times and Goulding himself taunted her by shouting “fake news” at the journalist.
A separate Ulster loyalist protest around the corner at the front of City Hall was held to demonstrate against dissident Irish republicans marching into the city centre to commemorate those who were interned without trial in Northern Ireland 46 years ago.
Unlike the Britain First Rally, Northern Ireland’s Parades Commission banned the dissident republican Anti-Internment League from central Belfast.
Twelve PSNI Land Rovers were parked across North Queen Street in the northern edge of the city centre to prevent about 400 republicans including two flute bands from filing into the heart of Belfast.
Behind the Land Rovers were several heavily armoured riot squad officers.
Banners were carried in the march in support of dissident republican prisoners held at the top-security Maghaberry prison outside Belfast and also which denounced “British internment”.
In previous years the anti-internment parade has proceeded through the city to be greeted by violence. At the same event in 2013, 56 officers were injured when loyalist protesters attacked the police.