Climate activist Greta Thunberg was among climate activists detained during protests against the demolition of the coal village of Luetzerath on Tuesday, according to police.

Thunberg was detained while protesting at the opencast coal mine of Garzweiler 2, some 9 kilometers (5.6 miles) from Luetzerath, where she sat with a group of protesters near the edge of the mine.

Thunberg, who joined the protesters on Friday, was seen sitting alone in a large police bus after having been detained, a Reuters witness said.

"We are going to use force to bring you to the identity check, so please cooperate," a policeman said to the group, according to Reuters footage.

"Greta Thunberg was part of a group of activists who rushed towards the ledge. However, she was then stopped and carried by us with this group out of the immediate danger area to establish their identity," a spokesperson for Aachen police told Reuters, adding one activist had jumped into the mine.

It was not yet clear what would happen to Thunberg or the group she was detained with, or whether the activist who jumped into the mine was injured, the spokesperson said.

Thunberg was carried away by three policemen and held by one arm at spotfurther away from the edge of the mine where she was previously sat with the group.

She was then escorted back towards police vans.