Gardai estimate the number of protesters to be 5,000. Protest organisers put the figure at 10,000.
Two protesters attempted to push their way through a security cordon but were pushed back by gardai.
People inside the Convention Centre have been told to move away from windows to avoid "antagonising the crowds".
A near riot broke out during the protests when a Fine Gael delegate who resembled Phil Hogan tried to pass through the crowd.
The man was engulfed by angry protesters and jostled before gardai came to his rescue.
As they attempted to escort him from the area they were surrounded by
screaming protesters, some of whom shouted “shame on you Hogan.”
The man was visibly shaken as he was put into a Garda squad car and driven away at speed.
Earlier a number of Fine Gael delegates who ventured through the crowd were also subject to verbal abuse