Four climate change activists protesting at a power station have been arrested, police said, while others were bitten by police dogs and suffered other injuries.
More than 1,000 demonstrators converged on the giant coal-powered Ratcliffe-on-Soar site in Nottinghamshire for a 24-hour "swoop", with clashes breaking out between police and protesters as they tried to tear up perimeter fencing.
Demonstrators, under the banner the Great Climate Swoop, included supporters of three pressure groups - the Camp for Climate Action, Plane Stupid and Climate Rush.
Chief inspector Linda McCarthy of Nottinghamshire police said: "There have been reports of some protesters receiving dog bites and other injuries as a result of a concerted effort to pull down fences and enter the site.
"Of course this is regrettable, but it's a combination of reckless behaviour by some of the protesters and us having to respond with a different style of policing."
One protester, Laura McFarlane-Shopes, 23, wore a bandage on her arm to cover a bite she had received from one of the dogs.
She said: "We were near the fence and some people were trying to get over. I was just in front of them. Horses and dogs started charging down. Police shouted that they were coming. They let the dogs on to me and one leaped up and bit my arm."
A police spokesman said: "We certainly haven't set dogs on anyone. Dogs have remained on their leads at all times. If people have received dog bites, that's regrettable, but dogs are a legitimate way of helping to maintain order."
The 2,000mw coal-fired power station is owned by the energy company E.ON and said to be one of the largest producers of carbon dioxide in Britain.
Activists hailed the protest as a "massive success".
