Irish Prime Minister Micheal Martin warned against a "spiral back" into sectarian conflict in Northern Ireland on Saturday, after a week of unrest.
Saturday marked the 23rd anniversary of the 1998 Good Friday Agreement, which wound down The Troubles – a decades-long conflict in the region that claimed 3,500 lives.
"We owe it to the agreement generation, and indeed future generations, not to spiral back to that dark place of sectarian murders and political discord," Mr Martin said.
"There is now a particular onus on those of us who currently hold the responsibility of political leadership to step forward and play our part and ensure that this cannot happen."
Police said disorder continued on Friday night, albeit on a smaller scale to clashes in Northern Ireland's capital Belfast earlier in the week.
Resentment among some of the pro-UK unionist community is simmering over concerns about trade barriers, following the UK's departure from the EU.
Checks have been imposed on some goods travelling from mainland Britain to Northern Ireland, as it has a border with EU member Ireland. Unionists fear an economic dislocation from the rest of the UK.
The violence has spread into the nationalist community, who want to be part of a united Ireland.
On Thursday night, nationalist rioters hurled petrol bombs, fireworks, bricks and bottles at armoured police vehicles, preventing their advance to a unionist area.
Officers deployed a water cannon for the first time in years and drove back the crowds late into the night.
On Wednesday night, the gates in a "peace wall" separating unionist and nationalist neighbourhoods were set alight.
Police said crowds from either side broke through to attack each other with petrol bombs, missiles and fireworks.
On Friday, marches had been planned in unionist communities in Belfast, but were cancelled following the news that Prince Philip, the husband of the UK's Queen Elizabeth II, had died.
"Protests are postponed as a mark of respect to the Queen and the Royal Family," a placard in one unionist neighbourhood announced.
