Protesters shut down well-known sites in central London as thousands of people in cities across the UK took part in rallies against Boris Johnson’s plans to suspend parliament.
Activists brought Trafalgar Square to a standstill with some sitting in the road as part of their demonstrations.
They also blocked Waterloo Bridge, shouting “stop the coup” and “our democracy and parliament is under attack”. Part of Whitehall was also shut.
Demonstrators outside Downing Street shouted “shame on you” in chants aimed towards the prime minister as streets around government buildings in Westminster were brought to a halt.
There were also protests in about 30 cities including Birmingham, Manchester, Newcastle, Liverpool, Glasgow, Swansea, Leeds, York, Belfast, Bristol and Aberdeen, as well as in towns including Bodmin in Cornwall and Clitheroe in Lancashire.
Mr Johnson is facing attempts by his parliamentary opponents to legislate against a no-deal exit from the EU, or to hold a vote of confidence in his government.
But he has insisted his rivals could be making the prospect of a withdrawal from the bloc without an agreement more likely.
In the coming days, Labour is expected to introduce a draft bill to try to block a no-deal Brexit and is being supported by Conservative MP Rory Stewart who claims around a dozen of his fellow Tories will also back it, defying their party’s leadership.
Shadow home secretary Diane Abbott told crowds in Westminster: “We cannot allow Boris Johnson to shut down parliament and to shut down the voice of ordinary British people.”
Speaking in Glasgow, her boss, Labour leader Jeremy Corbyn, said next week was the “last chance” to stop a no-deal Brexit.
He said: “Yes, it is the chance and we will do absolutely everything we can to prevent a no-deal Brexit and the prime minister taking us into the hands of Donald Trump and a trade deal with the USA.
“That is the real agenda of the prime minister. There is a lot of work being done in preparation for next Tuesday.”
Left-wing campaign group Momentum, which supports Mr Corbyn, has called on its members to “occupy bridges and blockade roads” in conjunction with unrest on the streets.
Among those protesting in Trafalgar Square was Terry who told Sky News that suspending parliament was “wrong” and “completely out of order”.
Terry admitted: “I don’t normally get involved in demonstrations and politics – but I think it’s a bit much.”
He said the government was “trying to shut down the debate completely just to get what they want” and “it made me feel a bit sick”.
The protests were triggered by the prime minister’s decision to suspend – or prorogue – parliament for up to five weeks ahead of the 31 October Brexit deadline.
Parliament will be prorogued in the week beginning 9 September until 14 October – the day of the Queen’s Speech.
Mr Johnson’s opponents have claimed the move was aimed at reducing Commons debating time to restrict MPs’ ability to block a no-deal Brexit.
Asked if he was denying opposition MPs the time to stop a no-deal withdrawal from the European Union, the prime minister earlier this week said: “No, that is completely untrue.
“We are bringing forward a new legislative programme on crime, hospitals, making sure we have the education funding we need.”
He added there would be “ample time” for MPs to debate Brexit both before and after a “crucial” Brussels summit of EU leaders on 17 October.