Climate activist Greta Thunberg was detained twice by Dutch police on Saturday after she and a group of marchers blocked a main road in The Hague to protest against fossil fuel subsidies.

Earlier, Thunberg joined hundreds of protesters on a walk from The Hague's city center 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 organized by the Extinction Rebellion environmental group (XR) — who previously swarmed the highway and blocked off traffic for hours before being sprayed by a police water canon and taken away.

On Saturday, 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 "The planet is dying!", chanting protesters were then locked in a tense standoff with police who formed a wall of law enforcement.

Thunberg joined in with the chants and slogans during the protest.

"It's important to demonstrate today because we are living in a state of planetary emergency," Thunberg told AFP as police blocked marchers.

"We must do everything to avoid that crisis and to save human lives," she said.

'Here for climate'

Some activists, however, found another route and blocked a main road close to the highway where they — including Thunberg — sat down on the tarmac. 

Asked whether she was concerned about police action and arrest, Thunberg said: "Why should I be?"

But shortly afterwards, Thunberg herself was arrested and dragged away by police to a waiting touring bus where she was detained with other activists.

She told the 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 said.

A spokesman for the Public Prosecutor's Office later confirmed the protesters were briefly detained before being released at a different location.

Shortly afterwards, however, Thunberg and some activists returned and were arrested again, this time for blocking a nearby traffic intersection, and led away to a waiting police van.

Prosecutor spokesman Vincent Veenman told AFP that currently no charges have been laid against the activists.

"This however may change if people are arrested over and over again for the same offence," Veenman said. 

Activists said that despite majority backing by the Dutch parliament as well as broad popular support to slash fossil fuel subsidies, "the plans will not be implemented before 2030, or even 2035".

"Meanwhile the ecological crisis continues to rage and the country's outgoing cabinet pretends that we have all the time in the world, while the crisis is now," XR said in a statement posted on X, formerly Twitter.

The protest, added XR, was part of a plan to pressure the Dutch government ahead of another planned debate about fossil subsidies in June.