German police on Thursday dismantled tree houses built by activists in a forest near the Dutch border to prevent an energy company from logging it for the purpose of expanding its coal mining activities in the area.

Riot police used cranes to bring down environmental activists who for five years had been living in tree houses in the ancient Hambach forest west of the city of Cologne, which was purchased by utility RWE decades ago for mining.

Most of the forest had already been logged down and activists were trying to prevent the remaining patch of green from facing a similar fate.

Representatives from RWE failed to reach an agreement during a meeting with activists on Monday to try to prevent the police evacuation.

The activists had asked RWE to delay the logging until a year-end deadline for a commission to submit plans to the government for an exit from coal-fired energy.

A police spokesman said measures were being taken to prevent the activists from returning to the site.

Germany aims to raise wind and solar power's energy share from a third now to 65 percent by 2030 to help to cut carbon dioxide emissions and achieve its climate commitments, in line with the wishes of the new coalition government.