Celebrities, political leaders and the masses have rallied in New York and across the globe demanding urgent action on climate change, with organisers saying 600,000 people hit the streets.

Hollywood actor Leonardo DiCaprio, UN chief Ban Ki-moon and New York Mayor Bill de Blasio all marched down Sixth Avenue on Sunday, in what was proclaimed the largest climate protest worldwide in history.

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There were also colourful and boisterous rallies in several other major cities in Latin America and Europe to as far away as India and Australia, designed to build pressure ahead of a climate-change summit hosted by Ban in New York on Tuesday.

In New York, where organisers said 310,000 people took part, elderly protesters – leaning on walking sticks and sitting in wheelchairs – joined young parents with children in pushchairs, adults in fancy dress and community groups.

“It’s very important. Our climate is killing us,” Coula Farris, an 88-year-old New Yorker, said.

There were chants of “hey, hey, ho, ho, fossil fuels have got to go,” as the colourful march snaked down Sixth Avenue with giant floats, balloons and banners with slogans such as “Urgent, Save our Planet”.

Very powerful ice sculpture melting on a muggy NYC morning pic.twitter.com/hto2GQeI8U

— Ken Kimmell (@kenkimmell) September 21, 2014

Ban, wearing a baseball cap and T-shirt with the words, “I’m for Climate Action,” praised de Blasio, who announced New York would reduce its greenhouse emissions by 80 per cent from 2005 levels by 2050.

The UN secretary general walked nine blocks in the parade with US former vice president Al Gore, who is now a climate advocate, de Blasio, French Foreign Minister Laurent Fabius and French Ecology Minister Segolene Royal, who wore a green suit and high heels.

“Our mission is to make this a decisive moment, a turning-point moment and I felt today that I was seeing history starting to be made,” de Blasio said.

In addition to New York, another 270,000 people turned out at about 2500 events around the world, organisers said.

In London, an estimated 40,000 people paraded past Trafalgar Square and the Houses of Parliament, including actress Emma Thompson, who likened the threat posed by climate change to a Martian invasion.

The pressure group Avaaz, which helped organise the rallies, said 30,000 people turned up in Melbourne and at least 15,000 in Berlin, where the crowd braved pouring rain, and another 5000 in Rio de Janeiro.

In Paris, where police estimated that 4800 people protested, many came on bikes with banners that read, “Climate in danger” or “World leaders, act!”

“Before we could say we didn’t know. Now we know. Climate change is already under way,” Nicolas Hulot, the French president’s special envoy for the protection of the planet, told the crowd.

In Madrid, hundreds gathered in front of the environment ministry, brandishing signs with slogans including “There’s no Planet B,” “Change your life, not your climate,” and “Our climate, your decision.”

In Cairns, Australia, where finance ministers from G20 nations were meeting, more than 100 people wearing green paper hearts around their necks gathered outside the venue.

Hundreds also massed in Sydney and in New Delhi.

Ricken Patel, executive director of Avaaz, presented a petition signed by two million people to Ban in New York.