The demonstration was organised to protest against fossil fuel subsidies in the Netherlands.
Police said more than 400 people were arrested on Saturday, including 12 for incitement. Activists later said Thunberg had been freed.
The 21 Swedish activist was initially detained by local police and held for a short time along with other protesters who tried to block a major highway into The Hague.
After being released, Thunberg quickly rejoined a small group of protesters who were blocking a different road leading to the railway station. There, she was detained a second time and driven off in a police van.
Veel van onze rebellen zijn gearresteerd (sommigen meermaals). Een paar rebellen zitten nog vast en we hopen dat ze snel vrij komen. Wij geven ons niet gewonnen.
Wij zijn niet te stoppen, fossiele subsidies wel.
Tot volgende keer op de #A12! #StopFossieleSubsidies pic.twitter.com/VUgduNI3PO
— Extinction Rebellion Nederland (@NLRebellion) April 6, 2024
Hundreds of protesters were marching from The Hague’s city centre to the nearby A12 arterial highway that connects the seat of the Dutch government with other cities including Amsterdam, Rotterdam and Utrecht.
The march was organised by the Extinction Rebellion (XR) environmental group and was part of a plan to pressure the Dutch government in the run-up to another planned debate about fossil subsidies in June.
Dozens of police officers, including some on horseback, blocked the group from accessing the motorway, warning that “violence could be used” should the marchers try to get onto the road.
Carrying XR flags and placards saying, “Stop fuel subsidies now!” and chanting “The planet is dying!”, protesters were then locked in a tense standoff with police who formed a wall.
‘Planetary emergency’
Before she was temporarily detained, Thunberg joined in with the chants and slogans.
She told journalists she was protesting because the world is facing an existential crisis.
“We are in a planetary emergency and we are not going to stand by and let people lose their lives and livelihood and be forced to become climate refugees when we can do something,” she said.
De nieuwe blokkade is door arrestaties beëindigd. #GretaThunberg werd er als bijna eerste eruit gehaald en apart vastgezet, terwijl bijna alle anderen in een stadsbus zijn gezet en meteen weer vrijgelaten. https://t.co/Y7UdsBDwPN pic.twitter.com/izizqNpxnh
— Extinction Rebellion Nederland (@NLRebellion) April 6, 2024
In recent months, the A12 road has been blocked for several hours dozens of times by activists demanding an end to all subsidies for the use of fossil fuels.
At previous protests, police drove detained protesters to another part of town, where they were released without further consequences.
Thunberg told the Netherlands’s ANP national news agency by telephone that her arrest had proceeded “calmly”.
“It’s not about the arrest. I am here for the climate,” she added.