Six people have been arrested outside City hall after demanding increased action on clean air from London Mayor Sadiq Khan.
The protest was organised by anti-pollution campaigners Stop Killing Londoners (SKL) and took place at 2.45pm on Monday (March 19).
Fourteen people, calling themselves Clean Air Defenders, dressed in black and white striped 'convict' suits for the protest, the group told getwestlondon.
Some spray-painted messages saying 'air pollution is criminal' on the walls of City Hall, on the South Bank, they said.
They also carried an enormous six-metre smog cloud banner.
SKL say six clean air defenders were arrested by police for criminal damage and taken into custody.
Scotland Yard confirmed six people were arrested on suspicion of criminal damage after its officers were called to a protest at 3.15pm.
SKL is calling on Mr Khan to formally submit to the proposals of the London Coalition for Clean Air - a network of groups representing communities across London, and meets with representatives within the next month.
The group has warned of more demonstrations to come in the coming days.
A spokesman said: “This action is the first of a series which will escalate through the week to send a clear message that London needs urgent action on air pollution.
“Unless the mayor agrees to meet with the coalition of community groups taking action on this issue clean air defenders have vowed to continue taking action and will risk a prison sentence.”
Police enquiries into the protest are continuing.
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