Taoiseach Simon Harris has expressed his disgust at “those flying the Irish tricolour whilst attacking police and spouting racism”.
Ireland’s premier spoke with Northern Ireland’s First Minister Michelle O’Neill on Sunday after violent scenes followed an anti-immigration protest in Belfast on Saturday.
Protesters waving both the union flag and the Irish tricolour took part in the protest at the front of Belfast City Hall.
There were also protesters in attendance from Coolock in north Dublin, which has been the scene of recent anti-immigration protests in the Republic of Ireland.
A statement from Mr Harris’s office said he had agreed to stay in contact with Ms O’Neill.
It said: “They discussed the violent scenes in Belfast last night and acknowledged the importance of the work between the gardai and PSNI to counter those who are trying to sow hate, racism and division in both jurisdictions on the island.
“The Taoiseach spoke of Belfast as a city and society that has spent decades working to reject hate, embrace peace, and build respect and inclusivity.
“The Taoiseach also expressed disgust at those flying the Irish tricolour whilst attacking police and spouting racism.
“This is repugnant to everything the Irish flag represents.”
There have been a series of anti-immigrant protests and incidents of related violence in the Republic of Ireland in recent months.
Ms O’Neill said: “I briefed An Taoiseach on the totally unacceptable racist attacks on people and businesses in Belfast yesterday.
“We are agreed that co-operation between the PSNI and An Garda Siochana is essential in bringing those responsible for the violence to justice and I urge anyone with information to bring it forward to the police.
“There can be no place for racism, hatred, discrimination and intimidation anywhere in our society.
“I remain resolutely committed to a shared, modern and inclusive society.”