About 200 anti-capitalist protesters linked to a group camped outside London's St Paul's Cathedral demonstrated on Saturday outside the parliament.
Protesters from the Occupy London Stock Exchange (OLSX) group had set off on a march towards Trafalgar Square but a breakaway group headed to the square outside the Houses of Parliament.
Scuffles broke out as police tried to block the demonstrators, some wearing Guy Fawkes masks that have become a symbol of their protest, from moving into the square but some managed to get in.
Scotland Yard said the protest was illegal, as the group had not been given the necessary permission to demonstrate outside parliament, and there were nine arrests for unlawful protest at the largely peaceful event.
But OLSX, who set up camp outside St Paul's in the heart of London's financial district on October 15, said it had been granted permission.
The protest was finished by about 9:00 pm (2100 GMT).
OLSX, a group inspired by an occupation of New York's Wall Street, said they were supporting around 20 young people who Saturday finished a march from northeast England to London, aimed at highlighting the effects of government cuts.