Hundreds of young people led by Swedish activist Greta Thunberg marched in Milan Friday to demand swift climate action a month ahead of the crucial COP26 environmental summit in Glasgow.

The Fridays for Future marches that brought large crowds of youth together in cities across the globe were interrupted by two years of the coronavirus pandemic. 

"We have to bring attention back to the huge issue that is the climate crisis," 15-year-old Maria told AFP, dressed in a white hazmat suit and green face paint.

"We are so happy to be back in the street," added the Italian teenager, marching under a giant wave of green cloth.

A few high-profile guests led the front of the parade including Thunberg and Ugandan activist Vanessa Nakate.

Both were in Milan as part of the official UN gathering for the youth version of the COP26 climate summit, to which 400 young people were invited.

"The world is waking up and change is coming whether you like it or not," read a sign in the crowd.

Other messages included the ever-popular "There's no planet B" or drawings of an ailing Earth with a thermometer in its cartoon mouth crying: "Save me". 

Some signs expressed thanks to Thunberg or quoted her infamous "How dare you?" speech at the UN General Assembly that went viral two years ago.

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Taking the microphone at the end of the march, Thunberg repeated her criticism of leaders who she says are all talk and no action.

"We see through their lies and their blah blah blah, and we are tired of it," she said, "hope is us: the people."

"We are the change together! Let's never stop, let's continue the fight," she added, while the crowd chanted "Greta!" in unison.

"We will not allow (ourselves) to be silenced," said Nakate before going on to list storms, floods and droughts that have cost lives across the African continent.

The march took place as ministers from several dozen countries gathered for meetings to prepare the COP26 summit in Scotland.

At their first session the day before, UN Secretary General Antonio Guterres once again called for urgent action to limit global warming to 1.5 degrees Celsius above pre-industrial levels -- the most ambitious goal of the Paris accord.

"I cannot emphasise enough that time is running out. Irreversible climate tipping points lie alarmingly close," Guterres told the ministers.

"We can either save our world or condemn humanity to a hellish future."