Organisers called for supporters to “return to Parliament Square” outside the Palace of Westminster from 6pm until late on Sunday.
Police have warned protesters they are banned from setting up camp at the landmark, as Scotland Yard insisted it had “an appropriate and proportionate police plan in place” for the event.
Dozens of officers were stationed in front of fencing placed around Parliament Square which prevented people from accessing the site.
A spokesman for the Metropolitan Police said it attempted to make contact with organisers but the group had “failed to engage” with the police force.
The force confirmed a Section 60 AA order was in place in the area around Parliament Square which gives police powers to force people to remove masks where they anticipate criminal activity.
The order is in place until 2pm tomorrow, a police spokesman said.
Activists will tonight begin a three day occupation of London’s Parliament Square to lobby for greater democracy.
The event, organised by campaign group Occupy London, is due to kick off at 6pm.
It will feature a series of guest speakers who will discuss subjects including the NHS, energy, the economy and the environment.
The three day gathering will be rounded off with a closing ceremony, due to start at 8pm on Sunday.
The three day event starting this evening in Parliament Square has been dubbed Occupy Democracy.
The organisers are hoping for a big attendance – and have used Twitter to get the word out.
A tweet issued from Occupy Democracy’s account shows a poster advertising the gathering complete with the following slogan: “Learn, discuss, participate.”
The organisers of Occupy Democracy have also used social media to give a brief explanation as to why they are protesting this weekend.
A post on Occupy London’s official Twitter account read: “Join us from 6pm at Parliament Sq.
“Be a part of the movement for genuine democracy – free from corporate influence.”
Among those attending tonight’s protest is Martin O’Flaherty.
He wrote on Twitter: “On coach to Victoria.
“Hoping @metpoliceuk behave themselves this weekend#occupydemocracy #tarpaulinrevolution #FreeNelsonMandela.”
The Met Police issued a statement earlier today ahead of this evening’s event in Parliament Square.
It read: “We are aware of an advertised event scheduled to take place between Friday, 21 November and Sunday, 23 November that involves an occupation of Parliament Square.
“Our Police Liaison Team has attempted to make contact with the organisers to discuss their plans for this event but so far the group have failed to engage with us.
“Parliament Square is governed by specific legislation and local bylaws which prevent anyone from putting up a tent or other structure, having anything with them for this purpose, or any sleeping equipment.
“It also prohibits the use of any amplified noise equipment.
“We continue to work closely with all the key stakeholders including Westminster City Council and the Greater London Authority around enforcement.
“We would encourage the organisers of the “occupy event” to contact our Police Liaison Team to discuss their plans.
“There will be an appropriate and proportionate policing plan in place.”
Tonight’s demonstration has the support of several Twitter users.
Among them is Emma Boucher, who tweeted: “Solidarity with everyone in Parliament Square tonight!
“Keep warm! #occupydemocracy.”
Pro-democracy protesters descended on central London tonight as the Occupy movement gathered to set up camp outside Parliament.
Organisers called for supporters to “return to Parliament Square” outside the Palace of Westminster from 6pm until late on Sunday.
Police have warned protesters they are banned from setting up camp at the landmark, as Scotland Yard insisted it had “an appropriate and proportionate police plan in place” for the event.
Dozens of officers were stationed in front of fencing placed around Parliament Square which prevented people from accessing the site.
Here is our first photo of the demonstration at London’s Parliament Square.
The image was posted on Twitter by a user known only as Bill.
It was accompanied by the message: “Numbers of protesters r increasing as is the police presence.”
A spokesman for the Metropolitan Police said it attempted to make contact with organisers but the group had “failed to engage” with the police force.
The force confirmed a Section 60 AA order was in place in the area around Parliament Square which gives police powers to force people to remove masks where they anticipate criminal activity.
The order is in place until 2pm tomorrow, a police spokesman said.
Protester Tom Kay, 21, from Sheffield, branded the police guard around Parliament Square “a disgrace”.
He said: “Protest is legal in this country and I think we should be able to protest where we want.
“The police are unwilling to let people protest seriously.”
Announcing the event on the Occupy website, a statement said: “We’re coming together because we want genuine democracy – free from corporate influence – where our voices count.
“Our votes, so hard won by the struggles of previous generations, have little value if politicians ignore the population they’re supposed to serve.”
There were a series of clashes with police on Parliament Square last month as supporters of the Occupy movement stood their ground for nine days. Green Party politician Jenny Jones was among a group of arrested protesters.
Under the Police Reform and Social Responsibility Act, the police can forcibly remove any protesters that decide to set up camp in Parliament Square.
The legislation was introduced after anti-war campaigners spent years occupying the London landmark outside Parliament.
About 100 protesters gathered at Parliament Square moved on to the road to form a blockade.
They unveiled a banner reading “real democracy now” and chanted “the police should be helping us”.
Long tailbacks quickly formed along Whitehall as frustrated motorists sounded their horns.
The protesters congregated peacefully on grassland opposite Downing Street amid a continued heavy police presence.
Author Donnachadh McCarthy, 55, said: “It’s outrageous that in Parliament Square free speech is being suppressed by Boris Johnson’s officers.
“If you don’t have free speech in front of Parliament, you don’t have free speech.”
Our live coverage of the Occupy movement setting up at Parliament is now concluded.
Pro-democracy protesters descended on central London tonight and called for supporters to “return to Parliament Square” outside the Palace of Westminster from 6pm until late on Sunday.
Police have warned protesters they are banned from setting up camp at the landmark, as Scotland Yard insisted it had “an appropriate and proportionate police plan in place” for the event.
Dozens of officers were stationed in front of fencing placed around Parliament Square which prevented people from accessing the site.
While our coverage here has ended keep viewing our website for any developments over the weekend.