London (AP) - British Prime Minister David Cameron on Thursday condemned violence that erupted during a demonstration against government plans to triple university fees, and police acknowledged they were unprepared for the mayhem.
Cameron said "the full force of the law" should be used against protesters who smashed windows, lobbed projectiles and stormed a London office tower housing the headquarters of his Conservative Party.
"People long in our history have gone to marches and held banners and made protests and made speeches and that's part of our democracy," Cameron said in Seoul, South Korea, where he is attending a G20 summit.
"What is not part of our democracy is that sort of violence and lawbreaking. It's not right. It's not acceptable and I hope that the full force of the law will be used."
More than 50,000 students, lecturers and supporters marched through London Wednesday against plans to raise the cost of studying at a university to up to 9,000 pounds ($14,000) a year -- three times the current rate -- in the largest street protest yet against the government's sweeping austerity measures.
Hundreds of demonstrators scuffled with police and burned placards outside Conservative headquarters as dozens stormed the lobby, scattering furniture, spraying graffiti and chanting.
Fourteen people, including seven police officers, were treated for minor injuries. Police said 50 people were arrested and bailed pending further inquiries.
Protest organizers condemned the violence by a minority, but images of masked protesters smashing windows dominated TV news bulletins and newspaper front pages on Thursday.
Metropolitan Police chief Paul Stephenson acknowledged that the force had failed to anticipate the violence, and initially had only 225 officers on duty to handle the crowd. He said it was "an embarrassment to London and to us."
"Certainly I am determined to have a thorough investigation into this matter," Stephenson said.
Cameron's government plans to triple tuition fees and cut funding to universities as it strives to slash 81 billion pounds ($128 billion) from public expenditure over the next four years.