More than a thousand environmentalists protested outside Tesla's factory near Berlin Saturday, police said, a day after some of them tried to force their way into the plant.

The protesters, accompanied by a large police contingent, unfurled anti-Tesla and anti-capitalist banners surrounded by a strong police presence. Organisers of the protest put their numbers at around 2,000.

While there were scuffles between some of the demonstrators and police at the beginning of Saturday's protest, the situation quickly calmed down, an AFP journalist noted.

Activists have been fighting plans to expand the factory at Gruenheide, which opened in 2022 following an arduous two-year approval and construction process dogged by administrative and legal obstacles.

They are made up of a collective of campaigning organisations including Extinction Rebellion and more local groups and the latest round of protests has been going on since Wednesday.

On Friday, police said they had driven back several groups of activists who tried to enter the factory. There were injuries on both sides, said a police spokesman, without providing figures.

Protests against the plant have increased since February, and in March the plant was forced to halt production following a suspected arson attack on nearby power lines claimed by a far-left group.

A week later, Tesla boss Elon Musk visited the site to lend his support to the staff and denounce what he said was the work of "eco-terrorists".

Tesla wants to expand the site by 170 hectares (420 acres) and boost production by up to one million vehicles annually to feed Europe's growing demand for electric cars and take on rivals shifting away from combustion engine vehicles.

The plant already occupies around 300 hectares, employing some 12,000 people. It produces the Model Y sports-utility vehicle, Tesla's main model for the European market.

But the Gruenheide site southeast of the German capital is near a protected forest and there are concerns about water use.

"People who live here are losing their means of subsistence because they no longer have drinking water," said Katja Kuehn, a 49-year-old activist. "The quality of the water is deteriorating."

"Globally, we also know that we don't need more electric cars," she said, adding that what was required was a totally different way of thinking about mobility.

Local residents voted against the project by 60 percent in a non-binding ballot in February.