Batons were drawn as gardai confronted a group of more than 50 Sinn Fein supporters who forced their way past the gates at Government Buildings yesterday.
The group, led by Sinn Fein TD Aengus Ó Snodaigh, had earlier protested outside Leinster House and then made their way from Kildare Street to Merrion Street shouting: “Cowen, Cowen, Cowen. Out, out, out!”.
Pressure on the gates forced them to open and Mr Ó Snodaigh and about 30 of the protesters rushed inside.
Some of them headed for a military police post where an armed corporal was on duty.
The corporal felt under threat and produced his baton to protect himself before he was supported by a garda motorcyclist, who also drew his retractable baton.
After a stand-off for a couple of minutes, the group was pushed back on to the street as garda reinforcements arrived on the scene.
Nobody was injured in the clashes and there were no arrests. But a garda investigation into the incident is now under way.
After the demonstrators had been escorted back on to Merrion Street, gardai maintained a blue line across the front of Government Buildings until the protest ended.
Speaking during the protest, Mr Ó Snodaigh said: “The Government, as usual, is targeting the least well off to pay for this mess. But they have absolutely no mandate for any of what they are doing. The Government should now publish its four-year plan, call an immediate general election and let the people decide,” he said.
Among those who took part in the protest were Sinn Fein vice president Mary Lou McDonald and Jim Monaghan, one of the Colombia Three activists.
In Cork, four members of Ogra Shinn Fein occupied the offices of Fianna Fail councillors at the City Hall while they also held a lunchtime protest outside the city's GPO.
Meanwhile, senior gardai are in close liaison with representatives of the ICTU in the lead-up to a massive street protest being organised for the centre of Dublin on Saturday.
The demonstration is expected by some of the organisers to attract at least 80,000 people but the final number could swell further as public anger boils over.
Gardai say they are adopting a low profile for the demonstration but will deploy sufficient personnel to ensure that it is policed properly.
The marchers will gather at Wood Quay and then head to O'Connell Street before staging an hour-long rally outside the GPO. The rally will include a number of speakers and music.