A day after climate strikes convulsed cities across the globe, with hundreds of thousands of young people opting to skip school and take to the streets instead, youth leaders have gathered at the United Nations to demand radical action on climate change.
The UN invited 500 young activists and entrepreneurs to take part in Saturday's meeting - the first of its kind - at the body's headquarters in New York.
It came days before a climate action summit scheduled to begin on Monday, which UN Secretary-General Antonio Guterres has called to seek greater commitments from world leaders on reducing their greenhouse gas emissions in line with the Paris accord to avert runaway global warming.
Among those in attendance on Saturday was 16-year-old Swedish activist Greta Thunberg, who started the climate strike movement with her lone protest in front of her country's parliament.
"We showed we are united and young people are unstoppable," she said.
Fellow activist Bruno Rodriguez, 19, who led school strikes in his native Argentina, warned that "climate and ecological crisis" was the "political, economic and cultural crisis of our time".
"Many a time, we hear that our generation is going to be the one in charge of dealing with the problems that current leaders have created, and we will not wait passively to become that future: the time is now for us to be leaders," Rodriguez said, watched by Guterres, who was billed as the "keynote listener".
The pair's comments came after masses of children skipped school on Friday to join global strikes that Thunberg said were "only the beginning" of the movement.
Some four million people filled city streets around the world, organisers said, in what was billed as the biggest-ever protest against the threat posed to the planet by rising temperatures.
Youngsters and adults alike chanted slogans and waved placards in demonstrations that started in Asia and the Pacific, spread across Africa, Europe and Latin America, before culminating in the United States.
Strike organisers 350.org said Friday's rallies were the start of 5,800 protests across 163 countries over the next week.
The protests will coincide with a landmark UN report due to be unveiled next week which will warn global warming and pollution are ravaging Earth's oceans and icy regions in ways that could unleash misery on a global scale.
But Guterres struck a more optimistic note on Saturday, telling youth leaders that "there is a change in momentum" on the issue of climate change.
"This changing momentum was due to your initiative and to the courage with which you have started these movements," Guterres said.
"Hold my generation accountable. My generation has largely failed until now to preserve both justice in the world and the planet," he added.
Al Jazeera's James Bays, reporting from the UN, said Guterres was hoping to capitalise on the "people power" seen on Friday and the leading role taken by youth activists, in particular, to fuel global action on climate change.
"What the UN are hoping is that they can leverage all of this public pressure with the mass protests and the youth summit to Monday," Bays said, referring to the upcoming climate action summit.