Irish riot police have clashed with students who had occupied the Department of Finance in Dublin city centre.
Gardai forcibly ejected students from the lobby of the Merrion Row building on Wednesday afternoon.
In violent scenes, at least one person was carried away, possibly unconscious. Others were visibly injured and bleeding.
The Union of Students of Ireland distanced itself from the violence.
The student protesters occupied the Department of Finance in a stand against plans to increase fees for third level education in the Republic of Ireland.
Several hundred students also staged a sit-down protest outside the building.
Earlier, thousands of students marched to Merrion Square, where they were addressed by student leaders.
The Union of Students of Ireland (USI) has warned that thousands of students would be forced to drop out of college if the registration fee rises again.
It has been suggested that the charge could rise from its current level of 1,500 euros to 2,500 euros.
USI President Gary Redmond said: "The organisation is deeply disappointed at the destructive behaviour of a minority of people at the Department of Finance, which occurred separately from the USI march.
"We do not condone destructive behaviour and believe that peaceful protest and open discussion and debate is the way forward for the students of Ireland."