Police arrested 153 people during clashes in London on the third day of protests against plans to raise student tuition fees.
The day ended with a stand-off with police in Trafalgar Square.
Demonstrations were held in cities across the UK - with occupations taking place in at least eight universities.
Meanwhile in Wales, the assembly government has announced its students will pay thousands less in fees than in England.
Business Secretary Vince Cable said he might now abstain in the vote on fees.
In Birmingham about 30 protesters occupied the city council's offices.
There were also protests in Leeds, Sheffield, Edinburgh, Liverpool, Belfast, Brighton, Manchester and Bristol, with school pupils joining students.
Students are campaigning against plans to raise tuition fees in England to up to £9,000 per year, with a vote expected in the House of Commons before Christmas.
The Welsh Assembly Government announced its own fee plans, which will see Welsh students at university in Wales and England paying no more than £3,290 per year.
It would mean that an English student at a university in England could pay more than £17,000 more for a three-year degree than a Welsh student on the same course.
Hundreds of protesters marched through central London in freezing conditions, but the numbers were smaller than the two previous demonstrations.
Demonstrators tried to avoid being caught in police lines, after thousands were held in a "kettle" last week.
Police eventually surrounded a group of around 150-200 people in Trafalgar Square, where fires were lit, graffiti daubed on statues and missiles thrown at riot police.
A police officer was taken to hospital with head injuries and three protesters were also hurt.
A 19-year-old student told the BBC their strategy was to avoid being contained by police: "Whenever the police block us off, we turn round and go the other way.
"We also do not want to be panicked into violence. Smashing up windows was necessary in the beginning to get the demonstrations on the front pages, but now any violence would be counter-productive."
Anger at Lib Dems
A total of 153 people were arrested during the course of protests in London.
Some 139 were arrested for breach of the peace, and seven with violent disorder, the Metropolitan Police said.
The National Campaign Against Fees and Cuts earlier accused the police of having "pre-emptively blocked" the protest route.
The Metropolitan Police say the marchers began earlier than planned and there was "never any intention to contain the protesters".
Protesters have directed anger towards the Liberal Democrats, whose MPs gave personal pledges to students that they would vote against any increase in fees.
But it remains uncertain whether Liberal Democrat ministers will abstain or support the proposals to raise tuition fees to £9,000 per year, when it comes to a vote in the House of Commons.
Vince Cable, the secretary of state responsible for universities, has indicated that he might not vote in favour of the fee rise, but might abstain.
Shadow business secretary John Denham says it would be "extraordinary and appalling" if the secretary of state did not vote for his own proposals.
As around 200 students held a protest outside the Sheffield offices of Lib Dem leader Nick Clegg, the leader of the National Union of Students, Aaron Porter, attacked the Liberal Democrats for failing to keep their promise to vote against raising fees in England.
"The anger felt at this betrayal is real, justified, and desperately disappointing to those who placed in you their hope for a different politics," said Mr Porter.
In Bristol, where thousands of students from both the city's universities marched, 10 people were arrested after police were pelted with mustard.
More than a thousand students protested in the centre of Manchester.
In Nottingham, about 150 protesters reportedly staged an occupation at the university and students said they held occupations at Kingston and Sheffield.
Sussex Police said around 100 protesters threw missiles from the roof of a car park in Hove, damaging buildings below.
And there were also demonstrations, marches, and occupations in Cambridge, Newcastle, Bath, and Cardiff.