Anti-capitalist protesters who have camped outside St Paul's Cathedral in London for more than one month refused to leave Thursday despite the expiry of a deadline issued by city authorities.

The City of London Corporation had a day earlier served the demonstrators with eviction notices giving them until 1800 GMT to pack up their tents and vacate a public road outside the historic church.

As the cathedral's bells struck six, a crowd of around 300 demonstrators at the foot of the steps of St Paul's waved their hands in what they described as a "silent scream".

The corporation, the local authority for London's financial district, will now go to court to start legal action for their removal, said John Cooper, the barrister for the Occupy London Stock Exchange movement.

"The city will be going to court tomorrow to start the process, with a High Court hearing on Wednesday. I think we'll have a clearer idea what will happen on Wednesday," he said in a statement to the crowd.

"You followed the legal advice you have been given and you have been respected for it."

Another lawyer for the protesters, Karen Todner, said she did not expect British police to emulate those in the United States, who demolished a packed protest camp near Wall Street in New York on Tuesday.

"The only way the police could remove you is if there was a public order incident, as far as I know there hasn't been any," Todner told the crowd.

Four policemen were posted on Thursday at the site. Protesters erected a banner saying "You can't evict an idea."

Dozens of colourful tents have been pitched outside St Paul's since October 15. The camp now also contains marquees including a food area and a so-called university.

But in the eviction notices pinned to some of the tents by council officers on Wednesday afternoon, the council said they were an "unlawful obstruction of the highway".

George Barda, a social justice campaigner who works for Greenpeace, said the protesters would stay on.

"Its the beginning of the legal process rather than the end. The hope obviously is that we do get a sympathetic judge that recognises that there are important issues that need to be discussed," the 35-year-old said.

Some of the tents are on public land but some are on cathedral property.

The camp has sharply divided authorities at the cathedral, which was forced to close for one week for the first time since World War II.

It suspended its part in the legal action against the activists and the third most senior clergyman at St Paul's, Dr Giles Fraser, resigned rather than see protesters forcibly evicted.

The head of the cathedral, Dean Graeme Knowles, later resigned citing the criticism he had faced over his handling of the debate.

In New York on Thursday, some 1,000 protesters converged outside the New York Stock Exchange amid a tense face-off with police, in a show of force by the Occupy Wall Street movement, which inspired the London protests.