Anti-capitalist activists have occupied an empty office block in London owned by Swiss banking giant UBS, their third protest site in the capital, the movement said on Friday.

The Occupy London Stock Exchange movement said a dozen demonstrators gained access to the building in the Hackney area of east London overnight and secured it, adding that they planned to use it as a "bank of ideas".

The London protesters, inspired by the Occupy Wall Street demonstrators in New York, also have camps outside St Paul's Cathedral in the heart of the fiancial district and in Finsbury Square, also near major banks.

"As banks repossess families' homes, empty bank property needs to be repossessed by the public," Occupy LSX member Jack Holburn said in a statement on the movement's website.

"We hope this is the first in a wave of ‘public repossessions’ of property belonging to the companies that crashed the global economy."

UBS said it was taking action, amid reports that security guards had turned up outside the building.

"We are aware of the situation and are taking appropriate action," it said in a statement.

London's Metropolitan Police had no immediate comment.

On Thursday night the protesters camped outside historic St Paul's refused to leave despite the expiry of a deadline issued by the Corporation of London, the local authority for the Square Mile.

The authority has said it will now take court action to evict the protesters, who have been camped outside the church for more than one month.