Environmental protesters who have blocked London roads and bridges for more than three days said Thursday they plan to take their civil disobedience campaign to Heathrow, Europes busiest airport, at the start of the Easter holiday weekend.

The Extinction Rebellion group said it would mount a protest at the airport on Friday. The group vowed to escalate its campaign of disruption if the British government doesnt step up action against climate change.

Heathrow said it was working with the authorities to address any threat of protests which could disrupt the airport.

Hundreds of demonstrators have blocked central London sites including Waterloo Bridge over the River Thames and the Oxford Circus and Marble Arch intersections since Monday.

The protest sites have sprouted tents, sound systems and even an ice cream van. Traffic is snarled and bus routes have been disrupted, to the frustration of commuters.

Police have made more than 420 arrests.

Extinction rebellion co-founder Gail Bradbrook said more people are joining us all the time.

Its certainly an option that tactics will be escalated if our demands are not met, she said.

Home Secretary Sajid Javid, Britains interior minister, condemned the demonstrations, saying protesters do not have the right to break the law and significantly disrupt the lives of others.

I expect the police to take a firm stance and use the full force of the law, Javid said.