1007 GMT October 15, 2019
It was expected to be the biggest protest ever against the threat posed to the planet by climate change, AFP reported.
Yelling slogans and waving placards, children and adults across Asia and the Pacific kicked off the protest, which spread later to Africa and Europe with huge crowds filling the streets.
"We are the future. We are schoolchildren and we are not going to school," said Vihaan Agarwal, 15, protesting in Delhi.
"We believe there is no point in going to school if we are not going to have a future to live in."
Organizers forecasted one million participants overall. In Australia alone, they said more than 300,000 children, parents and supporters rallied.
"Stop climate change now", "There is no planet B", "Wake up!" read some of the signs brandished by demonstrators in a trendy central shopping district of Tokyo.
Swedish schoolgirl Thunberg, 16, has accused leaders of not doing enough to prevent harmful climate change.
On the eve of the strikes, she insisted solutions were being "ignored".
The changing environment has become a daily fact of life in Australia, struck in recent years by droughts, more intense bushfires, devastating floods and the blanching of the Great Barrier Reef.
Numerous peer-reviewed scientific studies have shown a link between human-made gas emissions and climate change.
Friday's mass action set the scene for a range of high-profile climate events in New York.
A Youth Climate Summit will take place at the United Nations today.
UN Secretary General Antonio Guterres will then host an emergency summit on Monday in which he will urge world leaders to raise their commitments made in the 2015 Paris climate accord.
The agreement saw countries pledge to limit the long-term rise in the average temperature of the Earth to two degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial levels, and if possible, to 1.5 degrees Celsius.
A landmark UN report to be unveiled next week will warn that global warming and pollution are ravaging Earth's oceans and icy regions in ways that could unleash misery on a global scale.