Climate protesters and anti-cuts demonstrators have targeted a summit of major power firms over high energy bills and greenhouse gas emissions.
The Climate Justice Collective said 300 protesters attempted to disrupt the energy summit in the City of London in an event supported by groups including UK Uncut, Fuel Poverty Action and the Campaign against Climate Change.
The conference is being attended by bosses of the "Big Six" energy companies, which supply most of the power to UK homes and businesses.
The campaigners attempted to enter the venue of the conference with banners and giant model dinosaurs to highlight the "dinosaur technology" of fossil fuels.
They are angry at what they claim is a "stitch-up" by energy companies and the Government to maintain the current energy system, which they say is keeping bills high, pushing people into fuel poverty, and failing to tackle climate change.
Billie Blackwood, of the Climate Justice Collective, said: "It is corporate elites, including the Government, conspiring to keep the status quo of high energy prices, soaring profits, growing instability and disaster capitalism."
City of London Police said three arrests had been made for breach of the peace, and officers were containing the protest.