Four of the world's major cities have joined forces in the battle against climate change - agreeing to ban diesel cars from the streets within nine years.
By 2025, the high-polluting cars and vans will no longer be allowed in Paris, Athens, Madrid or Mexico City as mayors from each of the four cities vowed to be diesel-free by 2025.
It comes as temporary driving restrictions have been put in place by authorities in smog-hit Paris, as the French capital battles its worst air pollution in a decade.
Paris mayor Anne Hidalgo has led the initiative, speaking at last week's C40 conference of mayors on climate change in Mexico.
"Mayors have already stood up to say that climate change is one of the greatest challenges we face," she told the conference, adding:
London mayor Sadiq Khan has been called on to make a similar commitment to phasing out diesel vehicles in the city by 2025.
Campaigners have also demanded new clean air zones in all of the UK’s cities and major towns.
Soot from diesel vehicles is regarded as one of the biggest air pollution contributors, and the most harmful to human health - producing the gas nitrogen dioxide which can enter and lodge in the lungs.
Almost 500,000 premature deaths are attributed to air pollution in Europe every year and up to three million worldwide.
Mexico City's Mayor Miguel Ángel Mancera welcomed the agreement, and said increasing investments in public transport would also help clean the city’s air, and reduce greenhouse gas emissions.
Giorgos Kaminis, mayor of Athens, went one step further.
He said he would aim to remove all cars from the city centre completely in the same timescale. His city's authorities will also work with national governments and manufacturers to promote electric vehicles and cleaner transport, he added.