Around 70 police officers have been injured in environmental protests at a German village being razed to make way for a coal mine expansion, police said on Sunday.

In an operation that began on Wednesday, hundreds of police have been removing activists from the doomed hamlet of Luetzerath in western Germany.

The site, which has become a symbol of resistance to fossil fuels, attracted thousands of protesters on Saturday, including Swedish climate activist Greta Thunberg.

Some of the protesters clashed with police. The organisers reported that dozens had been injured. 

A spokesman on Sunday said the tally of police injuries was down to difficult conditions on the ground since Wednesday, as well as Saturday's clashes.

Criminal proceedings have been launched in around 150 cases, police said, including for resistance against police officers, damage to property and breach of the peace.

Activists on Saturday had accused the police of using "massive batons, pepper spray... water cannons, dogs and horses". 

At least 20 activists had been taken to hospital for treatment, said Birte Schramm, a medic with the group. Some of them had been beaten on the head and in the stomach by police, she said.

Organisers said that 35,000 protesters demonstrated on Saturday. Police put the figure at 15,000.

The situation on the ground was "very calm" on Sunday, the police spokesman said. 

About a dozen activists were still holed up in tree houses and at least two were hiding in an underground tunnel, according to the police.  

Luetzerath -- deserted for some time by its former inhabitants -- is being demolished to make way for the extension of the adjacent open-cast coal mine.

The mine, already one of the largest in Europe, is operated by energy firm RWE.

The expansion is going ahead in spite of plans to phase out coal by 2030, with the government blaming the energy crisis caused by Russia's invasion of Ukraine.