Irish PM warns of 'spiral' as unrest simmers in N.Ireland

Saturday marked the 23rd anniversary of the 1998 "Good Friday Agreement", which wound down "The Troubles" a decades-long conflict in the region which 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," Martin said in a statement.

"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 relative to clashes elsewhere in Belfast earlier in the week.

The most bitter unrest in recent years has mainly emanated from the pro-UK unionist community.

Resentment is simmering in some quarters over apparent economic dislocation due to Brexit and existing tensions with pro-Irish nationalist communities.

But the violence has since spread into the nationalist community in the divided British province.

On Thursday night nationalist rioters hurled petrol bombs, fireworks, bricks and bottles at ranks of armoured police vehicles preventing their advance to a unionist enclave.

Officers deployed a water cannon for the first time in years and drove back the surging 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 they were cancelled following the news that Prince Philip -- the husband of Queen Elizabeth II -- had died. 

"Protests are postponed as a mark of respect to the Queen and the Royal Family," a hastily erected placard in one unionist neighbourhood announced.