Northern Ireland’s power-sharing government put aside factional differences on Thursday to appeal for calm after more than a week of nightly violence partly fuelled by frustration among pro-British unionists about post-Brexit trade barriers.

Hundreds of youths in the United Kingdom province’s capital Belfast set a hijacked bus on fire and attacked police with stones on Wednesday in scenes reviving memories of decades of sectarian strife that killed some 3,600 prior to a 1998 peace deal.

The latest violence has injured 55 police officers and seen boys as young as 13 and 14 arrested on rioting charges.

“We are gravely concerned by the scenes we have all witnessed on our streets,” said the compulsory coalition, led by rival pro-Irish Catholic nationalists and pro-British Protestant unionists.

“While our political positions are very different on many issues, we are all united in our support for law and order and we collectively state our support for policing,” its statement added.

The violence comes amid growing frustration among many in the pro-British unionist community at new trade barriers between Northern Ireland and the rest of the United Kingdom that resulted from Britain’s exit from the European Union.

The pro-British Democratic Unionist Party (DUP) has also pointed to a decision by police not to prosecute Irish nationalists Sinn Fein for a large funeral last year that broke COVID-19 regulations.

Sinn Fein in turn has blamed the DUP for stoking tensions with its staunch opposition to the new trading arrangements and a call in recent days for the region’s police chief to step down.

The Police Service of Northern Ireland has said some of the violence was influenced by “criminal elements” who helped to orchestrate the attacks.

The violence on Wednesday took place near the Shankill Road in west Belfast near a so-called “peace wall” that divides the community from the Irish nationalist stronghold of the Falls Road, where groups of youths also gathered.

The walls and fences were built between the two communities to prevent clashes during three decades of sectarian violence in Northern Ireland that largely ended with a 1998 peace deal.

The leaders of Northern Ireland’s largest political parties Sinn Fein and the DUP both condemned the violence, pointing in particular to the bus hijacking and an attack on a photojournalist from the Belfast Telegraph newspaper.

“These actions do not represent unionism or loyalism. They are an embarrassment to Northern Ireland,” DUP leader Arlene Foster wrote in a Twitter post that went on to describe rivals Sinn Fein as “the real law breakers.”