GRETA Thunberg expressed her disbelief as hundreds of thousands of people – from Canberra and Kabul to Cape Town and Berlin – took to the streets to demand world leaders tackle the climate crisis ahead of a key UN summit.

The teenage Swedish activist said she never imagined it would take off so quickly, as youngsters across the world missed school to take part in the second event of its kind this year.

The protests can be traced to the 16-year-old, who has staged weekly demonstrations over the past year in Stockholm under the heading Fridays for Future. She is expected to speak at the UN Climate Action Summit on Monday.

Thunberg called the mass demonstrations “a victory”, adding: “I would never have predicted or believed that this was going to happen someday and so fast.” She added it was now up to world leaders to take action and if they do not, they should “feel ashamed”.

The global event began in Australia, where an estimated 300,000 protesters marched in 110 towns and cities, including Sydney and the capital, Canberra.

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Demonstrators called for their country, the world’s largest exporter of coal and liquid natural gas, to take more drastic action to reduce greenhouse gas emissions. If estimates are correct, it was the country’s biggest demonstration since the Iraq War in 2003.

Hundreds of other rallies took place across Europe, including in the Czech Republic, Germany, and Poland.

In Berlin, organisers said 80,000 people gathered in front of the capital’s landmark Brandenburg Gate, not far from Chancellor Angela Merkel’s office, where her cabinet was thrashing out the final details of a plan to curb Germany’s greenhouse gas emissions.

Meanwhile, an estimated 100,000 protesters joined an event in London, with another 10,000 in Brighton. Demonstrations were also staged across Wales and all of Ireland.

Smaller protests took place in Asia, including in Japan, South Korea, the Philippines, Hong Kong and India.

In Africa, rallies were held in Johannesburg and the South African capital Pretoria, as well as Kenya’s capital Nairobi.

Experts say Africa is the most vulnerable continent to climate change and the least equipped to deal with it. Governments have pleaded for more support from the international community.

A further 800 rallies were scheduled to take place in the US.