Two people have been injured after a republican parade through Belfast city centre passed with only minor trouble.
Plastic bottles, fireworks and coins were thrown by a small group of protesting loyalists along the main shopping street but the event was largely peaceful. Police said an officer and a member of the public were slightly hurt.
Unionists were objecting to nationalists marking the anniversary of the introduction of detention of terrorism suspects without trial by the Army during the height of the Troubles, still a republican grievance more than 40 years later.
Dozens of riot police wielding shields with batons in holster formed a barrier between the opposing groups on Royal Avenue and there were some verbal exchanges. Republicans waved Irish flags and held banners calling for the "End of British Internment" while loyalists clutched Union flags.
Metal security force barricades were erected throughout the city centre's side streets, heavily armoured police Land Rovers were parked at almost every corner and large white water cannon vehicles and police dogs were on standby for trouble.
Police Service of Northern Ireland (PSNI) assistant chief constable Mark Hamilton said: "Today's parade and associated protests passed off with minor trouble, with a number of fireworks and missiles thrown as the parade passed through Royal Avenue. One officer and one member of the public are reported to have each sustained a minor injury.
"There was a considerable policing operation put in place throughout the city centre today to ensure that the Parades Commission determinations in respect of the parade and the associated protests were upheld. Our focus was, as always, on keeping people safe."
Police will review evidence surrounding any potential offences or breaches of rules set by the Commission, which adjudicates on where contentious marches can go and which symbols or music can be used.
At the same event last year 56 officers were injured when loyalist protesters attacked them.
Marches this summer, the majority by loyal orders, have been almost exclusively peaceful after a broad coalition of unionists appealed for calm.
But political relations at Stormont, the devolved power sharing Executive, soured in recent months following the failure to reach agreement on key peace process issues including parades.
Sinn Fein president Gerry Adams said on Friday the political process faced its greatest challenge since the 1998 Good Friday peace agreement which ended IRA violence and led to the establishment of the devolved institutions.
Mr Adams said he was not hopeful that a fresh round of all-party talks which the Irish Government wants to see beginning next month could resolve outstanding issues hanging over from the peace process. Those include dealing with the legacy of conflict violence and issues over contentious parades and flags.
Democratic Unionist Party First Minister Peter Robinson, whose party is in coalition with Sinn Fein, has said the issue most likely to bring down the ministerial Executive was failure to agree on welfare reform cuts which have seen the Treasury threaten to reduce the amount it pays to fund Northern Ireland public services.
In recent days devolved ministers have warned street lights may not be repaired and the expansion of the University of UIster in Londonderry may be taken off the table as a consequence of the disagreement over welfare.
Changes include the so-called spare bedroom tax, which Sinn Fein argues will hit the poorest hard but which the DUP favours implementing rather than facing large fines from Westminster.