Several police officers have also been injured in the violence in the Northern Irish capital, which has lasted several days.

The violence happened on both sides of an interface in the loyalist Shankill and nationalist Springfield Road areas. The two sides clashed across the wall, while nearby a city bus was hijacked and set on fire.

A bus was set on fire in the Lanark Way area of west Belfast on Wednesday, while petrol bombs, bricks and bottles were thrown at police - and a press photographer was assaulted.

Others have attempted to characterise the violence on Brexit and Boris Johnson's failure to spell out the implications of the Northern Ireland Protocol and the trade disruption that has resulted in the wake of the transition period.

Northern Ireland has seen sporadic outbreaks of street violence since the 1998 Good Friday peace accord ended the Troubles - decades of Catholic-Protestant bloodshed over the status of Northern Ireland in which more than 3,000 people died. Britain's split from the European Union has renewed tensions over Northern Ireland's status and disturbed the political balance in region, where some people identify as British and want to stay part of the United Kingdom, while others see themselves as Irish and seek unity with the neighbouring Republic of Ireland, an European Union member.

"They are an embarrassment to Northern Ireland and only serve to take the focus off the real lawbreakers in Sinn Féin".

My Government has listened to and will continue to listen to and engage with the views of all communities in Northern Ireland.

We should all know that when politics are perceived to fail, those who fill the vacuum cause despair.

The British-run region's devolved executive, a compulsory power-sharing coalition led by Irish nationalists and their unionist rivals, will meet later on Thursday to discuss the clashes, Deputy First Minister Michelle O'Neill said.

"But the paramilitary godfathers behind this really don't care; they will exploit these young people for their own ends". The controversy stirred the old conflict in Northern Ireland, between separatists and loyalists.

Alliance party leader and justice minister, Naomi Long, said there had been "inflammatory rhetoric with threats of renewed violence bandied around by people who claim to be trying to lead others away from the violent past". But unionists say the new checks amount to a new border in the Irish Sea between Northern Ireland and the rest of the U.K. They fear that undermines the region's place in the United Kingdom and could bolster ties with the Irish Republic, strengthening calls for a united Ireland.

While Mrs Foster has accused the Police Service of Northern Ireland of undermining the rule of law and called for the resignation of the chief constable, critics have sought to blame the unrest on the DUP's inflammatory language.

The DUP in turn have pointed to a decision by police not to prosecute Irish nationalists Sinn Fein for a large funeral past year that broke COVID-19 regulations.

Regarding the bus attack in Belfast, she added in a subsequent post on Twitter: "This is not a protest". The funeral of Bobby Storey drew a large crowd, despite coronavirus rules barring mass gatherings. "There's many factors, including, obviously, criminal gangs at work who benefit from chaos like this".