Tens of thousands of demonstrators, including many young activists, turned out for rallies across Australia Friday, kicking off what is expected to be a worldwide series of protests to demand action on climate change.

More than 800 marches were planned on Friday in the United States, expected to draw on thousands of young people skipping school. Swedish teenage activist Greta Thunberg, the figurehead of the climate school strike movement, is expected to attend a rally in New York’s Thomas Paine Park.

Similar rallies were planned in the United Kingdom, France and Germany and more than two dozen other countries.

The protests, billed as a “global climate strike,” come ahead of a planned U.N. Climate Action Summit that begins in New York on Monday. In March, a similar protest inspired by Thunberg drew crowds around the world including thousands of young students who skipped school to attend.

Organizers say some 100,000 people gathered in Melbourne, with at least 50,000 more in Sydney and thousands more in the capital, Canberra, as well as Perth, Brisbane and Adelaide, among other Australian cities.

The numbers of participants could not be immediately verified.

In Sydney, Moemoana, 18, came from Wollongong to protest on behalf of her native Samoa, one of thousands of low-lying islands around the world that are particularly threatened by rising sea levels due to climate change.

“The Pacific Islands are meters above sea level because of climate change and it’s a scary future for our islands,” she was quoted by The Guardian Australia as saying. “We want to urge people to take some action.”

Australia is the world’s largest exporter of coal and liquefied natural gas – both major contributors to greenhouse gas emissions. Protesters marched to demand that government and businesses commit to a goal of net zero carbon emissions by 2030.

Australian Prime Minister Scott Morrison, who is in the U.S. for a state dinner with President Trump, has been criticized for not including the U.N. climate summit on his itinerary.

At least 2,000 companies in Australia gave employees time off to attend the rallies, according to The Sydney Morning Herald. Meanwhile, the country’s acting prime minister, Michael McCormack, speaking in Melbourne, expressed displeasure with students attending the protests.

“These sorts of rallies should be held on a weekend where it doesn’t actually disrupt business, it doesn’t disrupt schools, it doesn’t disrupt universities,” McCormack told reporters according to The Associated Press.

In Kirabati, a Pacific island chain that experts fear could be inundated by sea level rise in the next 25 years, some signs carried by protesters read: “We are not sinking, we are fighting.”

Some 200 young activists marched to the Ministry of Environment in Bangkok, Thailand, where they dropped to the ground in mock death to demand that the government declare a climate emergency.

“We’re young, but we’re not dumb. We know it’s happening. We need change. We demand better,” 11-year-old Ralyn “Lilly” Satidtanasarn told The Bangkok Post.

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