The three camps, each of them in the heart of the cities' financial districts, sprang up a day after rallies in 80 countries inspired by the "Occupy Wall Street" movement and Spain's "Indignants" campaign.
In London, several hundred anti-capitalist demonstrators camped in front of St Paul's Cathedral, just metres (yards) away from the London Stock Exchange, under the tolerant gaze of the Reverend Dr Giles Fraser.
Asked about the protesters bedding down for a second night Fraser, Canon Chancellor of the cathedral, said: "We'll see how it goes.
"We're taking one day at a time and it's really good to see it's all worked out well for us today," he added.
Roy Alexander, 39, who acted as an organiser for the occupation on the first day, said: "We're planning to stay here indefinitely.
"We'll stay here and make a stand. I think we'll have more people join.
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The camp had already grown to about 70 tents late Sunday. A long table filled with cake, biscuits and bottles of water se