John Duffy, registrar and secretary of the university, called the violent nature of the protest “shocking and appalling” and labelled student organisers “irresponsible”.
The day had begun peacefully with speakers in the campus’s Library Square.
Among those talking were North Ayrshire and Arran MP Katy Clark and Alfie Meadows, who suffered serious injuries in the 2010 student protests.
Brighton Pavilion MP Caroline Lucas also had a statement read on her behalf.
Following the rallying calls, the protesters began marching around the campus’s scattered buildings, lighting flares and fireworks and carrying banners.
At Sussex House security staff had boarded up windows and organised for police to stand on the other side of the glass doors.
Within minutes the mood of the march turned ugly and activists in balaclavas began to smash the glass with placards and sticks.
Dozens of police officers moved in to try to disperse the crowd but after a line of protesters met them face on and coins began to be hurled, they withdrew to put on riot gear.
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They then stood and watched as around 100 protesters smashed their way into Sussex House, set up barricades with furniture and began looting.
One masked activist who had sprayed “Occupy” in yellow paint in the stairwell of the building, said: “It was originally going to be a peaceful student protest. As per standard it escalates a little bit.”
A small group grabbed a pile of admin folders and set fire to them outside the entrance as they tried to hold off police.
The students withdrew to their original occupation point at Bramber House where some smashed through a second section of the top floor to take control of more of the building.
Meanwhile, just 100 metres from Sussex House, a female student was lying unconscious at the bottom of concrete steps.
Onlookers said that she had collapsed and was known to have a heart condition. She was speaking to paramedics as she was loaded into the ambulance.
Mr Duffy said: “We cannot tolerate today’s violent behaviour. There is no excuse.”
A police spokeswoman said that no arrests were made and that there were no injuries.
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