By Victoria Klesty and Gwladys Fouche

OSLO (Reuters) -Environmental campaigner Greta Thunberg and dozens of other activists on Monday blocked entrances to Norway's energy ministry, protesting against wind turbines built on land traditionally used by indigenous Sami reindeer herders.

Thunberg, a vocal advocate for the ending the world's reliance on carbon-based power, said the transition to green energy could not come at the expense of indigenous rights.

"Indigenous rights, human rights, must go hand-in-hand with climate protection and climate action. That can't happen at the expense of some people. Then it is not climate justice," Thunberg told Reuters while sitting outside the ministry's main entrance with other demonstrators.

Norway's supreme court in 2021 ruled that two wind farms built in central Norway violated Sami rights under international conventions, but the turbines remain in operation more than 16 months later.

Reindeer herders in the Nordic country say the sight and sound of the giant wind power machinery frighten their animals and disrupt age-old traditions.

"We are here to demand that the turbines must be torn down and that legal rights must be respected," said Sami singer-songwriter, actress and activist Ella Marie Haetta Isaksen.

She and a dozen other Sami demonstrators had occupied the ministry's reception area since Thursday. Police forcibly removed them around 0130 GMT on Monday and detained them before releasing them.

They returned to the ministry, this time outside, around 0600 GMT.

The Sami protesters wore their traditional costume, often called gakti, inside out as a sign of protest.

The ministry said the ultimate fate of the wind farms is a complex legal quandary despite the supreme court ruling and is hoping to find a compromise.

The court's verdict did not say what should happen next to the 151 turbines, which can power some 100,000 Norwegian homes, or what should happen to the dozens of kilometres (miles) of roads built to facilitate the construction.

"We understand that this case is a burden for the reindeer herders," Minister of Energy and Petroleum Terje Aasland said in a statement to Reuters.

"The ministry will do what it can to contribute to resolving this case and that it will not take longer than necessary," he added.

Owners of the Roan Vind and Fosen Vind farms include Germany's Stadtwerke Muenchen, Norwegian utilities Statkraft and TroenderEnergi, as well as Swiss firms Energy Infrastructure Partners and BKW.

"We trust that the ministry will find good solutions allowing us to continue the production of renewable energy while maintaining the rights of the reindeer owners," Roan Vind said in a statement.

Utility BKW said it expected the wind turbines to remain in place, with compensatory measures to ensure that the rights of the Sami reindeer herders are guaranteed.

Stadtwerke Muenchen declined to comment.

Statkraft and Energy Infrastructure Partners were not immediately available for comment.