Groups in Germany, France, Hungary, Australia, New Zealand, Austria, the Netherlands and Spain attempted to build barricades or block traffic by sitting on the road.
London police say they arrested members of the group as they blocked Victoria Embankment, outside the Ministry of Defense.
The group aims to remain peaceful.
"We will have a visible presence to keep the peace, provide a safe environment, and limit any negative impact on the general public", said Roed.
Over in Madrid, the climate activists blocked roads and staged a sit-in.
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Earlier Monday, hundreds of activists with the same movement blocked a central square in Paris.
"There will be disruption for sure, but we have tried to minimize it as much as possible", said Extinction Rebellion Vancouver spokesperson Edison Huang, adding he's informed transit officials and police of the demonstration plans.More news: CIBC Run for the Cure this Sunday
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"The government did not act on Parliament's declaration of a climate and environmental emergency". We can't any longer allow governments to do this so we have to make it clear that there is no more time.
"The figures I saw, we were the best in the G7".
"This is not just a problem for the United Kingdom, this is directly affecting communities in the global south, and we need to recognise the responsibility we have as the birthplace of the industrial revolution".
The movement is partially credited with pushing the United Kingdom government in June to become the first in the Europe Union to commit itself to a net-zero target for harmful emissions by 2050.
Meanwhile activists in London, some wearing yellow safety helmets with "Rebel at Work" painted on the side, glued or chained themselves to cars parked in the middle of roads or to street lamps, making it hard for police officers to detain them. The movement had announced two weeks of protests with plans to occupy main roads and "paralyse" the German capital and other major cities around the world, starting on 7 October. "What this means is that the government would rather arrest people than take real action on climate change", one protester told CP24 on Monday afternoon.
In Calgary, about 50 people took to the intersection of 10th Street N.W. and Memorial Drive N.W. between 4 p.m. and 6 p.m., with some wearing gas masks and clanging bells, and others holding handmade signs.
"We came down for the Extinction Rebellion protest which is trying to shed light on the fact that governments are seeming to keep their heads in the sand about climate crisis", said Tal Ponany.
Protesters waved colourful flags and carried a large pink banner with the words: "This is a climate emergency, act like it".
"I'm scared for that future and I'm here out of love for life and the animals that have gone extinct and everyone's voice that has been silenced because they were not heard in time". If violence was used or critical infrastructure such as the airport became affected, the police would have to intervene, he said.
Extinction Rebellion protesters took to 60 bridges around the world Monday under a campaign called #BridgeOut. The protest went ahead despite a city ban on activists gathering on the road.
Three protesters have been arrested in Sydney.