A parade by republicans through Belfast saw minor disturbances as it proceeded through the city centre amid dreadful weather and a vast police presence.
As well as the contentious march, which was to mark the anniversary of the introduction of internment without trial in 1971, there were counter-demonstrations by loyalists objecting to it.
Some loyalists in the CastleCourt area, separated from the marchers by police lines, could be seen shouting and gesturing as the parade passed.
Meanwhile, some in the parade could be spotted doing the same towards the loyalists.
The PUP called for an investigation after a video emerged showing a number of those at the rear of the parade apparently engaged in pro-IRA chanting: http://www.youtube.com/watch?v=QEGsAHJPQkA&sns=em
Police said fireworks and missiles had been thrown and that one officer and one member of the public had been injured.
The republican organisers told the Parades Commission that up to 4,000 would be participating in the march from north Belfast to the city centre, which set off at around 1pm.
The PSNI spokeswoman would not comment on the actual numbers estimated to be involved, saying this was a matter for organisers.
Some of the republicans participating could be seen sporting dark-green or black berets.
The PSNI announced it would now be reviewing all the evidence it has gathered to see if any offences or breaches of the Parades Commission determinations had happened.
One of the determinations around the march was that “no paramilitary-style clothing” was to be worn.
One of the reasons loyalists have found the parade so objectionable is that it passed an area where two UDR soldiers had been killed by republicans in 1988.
Last year, violence flared at the same demonstration, with cars burnt out on Royal Avenue.
Much of the city centre had been closed during the march.