Hundreds of police officers have descended on a patch of forest in western Germany occupied by activists living in treehouses, in a major escalation of a long-running environmental battle.

Dozens of protesters have occupied 60 treehouses, some as high as 25 metres off the ground, since 2012 in an attempt to protect the ancient Hambach forest from being felled to make way for the expansion of an open-pit coal mine.

Until now their presence has been quietly tolerated, but police moved in after local authorities ordered that the forest be cleared immediately, citing fire hazards.

Protesters have built a camp with tents and treehouses to stop the clearing of the Hambach forest for open-cast coal mining. Photograph: Wolfgang Rattay/Reuters

The state premier of North Rhine-Westphalia, Armin Laschet, told broadcaster WDR on Wednesday that the forest was being “illegally occupied” and accused the protesters of being violent.

The activists, who are protesting the expansion of the energy giant RWE’s massive open-pit lignite mine, one of Europe’s largest, have called for a mass mobilisation of supporters in coming days.

“The destruction of Hambach forest is intolerable,” said Jan Puetz, of Aktion Unterholz, in a joint statement with other activist groups. “Starting this weekend, we will prevent the evacuation and the forest-cutting by police and RWE with actions of mass civil disobedience.”

State police warned on Twitter that the height at which the demonstrators were hunkering down “poses a danger to EVERYONE. We don’t want people to get hurt”.

A live video, streamed on Spiegel Online, showed officers in a cherrypicker cutting down branches to gain access to the homemade structures. A large rescue air cushion was placed on the ground.

Police moved in after local authorities ordered that the Hambach forest be cleared immediately, citing fire hazards. Photograph: Henning Kaiser/AFP/Getty Images

Officers also peacefully broke up a sit-in by a group of demonstrators blocking the path to the treehouses and removed makeshift barriers, according to DPA news agency.

As well as a significant police presence, heavy clearing equipment and water cannons could be seen at the site.

The battle has been intensifying for days after RWE announced its plans to clear half of the forest’s remaining 200 hectares from mid-October.

A police officer fired a warning shot in the forest on Wednesday, Aachen police said in a statement, after “several masked people once again attacked police by throwing stones”.

RWE owns the forest and is legally allowed to cut down trees to access the brown coal, or lignite, in the ground during the annual logging season.

It says the clearing is necessary to ensure energy supply, including of nearby power plants.

But activists oppose the use of the cheap but polluting fuel, and say the forest is home to protected species like Bechstein’s bat and century-old beech and oak trees.

Workers begin clearing treehouses from an area of the Hambach forest. Photograph: Thilo Schmuelgen/Reuters

Their protest has taken on fresh urgency as Germany is charting an exit from coal energy to combat climate change. A government-appointed coal committee is due to announce an end date for the industry by the end of the year.

Germany has massively expanded renewable energy in recent years as part of its “energy transition” away from fossil fuels.

But the country remains heavily reliant on coal, partly to offset Chancellor Angela Merkel’s 2011 decision to phase out nuclear power by 2022, and the government admitted in June that it will miss a 2020 target for reducing carbon dioxide emissions.

The environmental group Greenpeace accused the German government of standing by and allowing “RWE to dangerously fuel the social conflict” in Hambach forest, even as the coal industry was in its death throes.

“Merkel must now de-escalate and halt further clearing, until the coal commission has finished its work,” said its spokeswoman Gesche Juergens.

Agence France-Presse

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