Water cannons were used for the first time by gardaí on Saturday evening against protesters marching to the Phoenix Park in Dublin where the Taoiseach was hosting a dinner for EU leaders at Farmleigh House.
The stand-off between gardaí and protesters who had marched from the GPO to the Ashtown gate area near the park, degenerated into a physical confrontation between a small band of demonstrators and the Garda riot squad, protected by Perspex shields and supported by two water cannons.
Missiles, mostly cider cans and plastic bottles, were hurled at the Garda lines.
At some stages, it appeared that a full-scale riot could ensue. A small number of gardaí briefly drew their batons and struck protesters.
Ultimately, gardaí held their lines with relative ease and gained control of the situation in less than half an hour, settling into a pattern of firmly pushing the protesters down the Navan Road towards the city centre.
Gardaí had chosen to block the path of the protesters at the Ashtown Roundabout, on the Navan Road, close to the Ashtown gate into the Phoenix Park.
For two hours senior officers had observed the march as it made its way from O'Connell Street towards the park.
Gardaí believe around 1,500 people were on the march. Dublin Grassroots Network, which organised the protest, put the figure at between 3,000 and 5,000. The protesters had been warned by gardaí not to march. At O'Connell Street at 6.30 p.m., the organisers decided to proceed with the protest following a "demonstration of democracy" when they asked the crowd whether they should continue with a march.
For the most part, the marchers were good natured and in high spirits. But in the crowd, were more than 20 people hiding their faces with balaclavas, masks and scarves. A small number had been drinking alcohol throughout the day.
As the march progressed along the Navan Road, the organisers stopped it around 500 metres before the Ashtown Roundabout, after it became apparent gardaí were blocking their way.
The Garda Commissioner, Mr Noel Conroy, and the Deputy Commissioner, Mr Fachtna Murphy, were personally overseeing the Garda operation, and were standing just 100 metres behind the Garda lines.
Just after 8.30 p.m., a group of 100 protesters moved towards the uniformed Garda line, chanting slogans.
Meanwhile a second group of protesters, headed by a group of around 20 masked individuals wearing black and holding a banner, began to move forward towards the Garda line, soon pushing the other group of protesters against the gardaí.
Projectiles were also thrown, one of them hitting a female garda on the head. She was helped back by her colleagues. The riot squad and two water cannon then arrived on the scene. Gardaí soon gained control and began pushing the protesters back down the Navan Road and made several arrests.