Anti-coal activists in Germany mounted a blockade of a controversial brown coal mine on Saturday, occupying a rail line connecting the mine to factories.

Police said around 2,500 environmentalists blocked a rail line connecting the mine to factories and other processing facilities by sitting on tracks, chanting "we are unstoppable, another world is possible."

Parts of a German motorway nearby were blocked for several hours as police fired water cannon on protesters who had broken police lines in an effort to access the Hambach surface mine in western Germany.

Eight environmentalist had also climbed on top of an excavator at the mine, with another 30 activists blocking access to the digger. Police used pepper spray and batons to keep another 250 from entering the mining site.

The mine is located at Hambacher Forest, where nearly 3,900 acres of historic woodland, with protected animal species and centuries-old trees, have been felled for access to brown coal, prompting protests.

Police say they are expecting a major blockade of more diggers, as well as coal tracks and conveyor belts, over the weekend. "We'll take care of it," a police spokeswoman said.

The environmentalist group Ende Gelaende planning the blockade said more than 6,500 protesters had taken part in the demonstration.

Energy company RWE's plans to cut down more than half of the remaining forest near the mine to dig up more coal were halted earlier in October by a court order to review endangerment of animals living in the forest.