The early part of the demonstration, organised by the Extinction Rebellion (XR) group, coincided with a police strike over pensions.

But the strike ended at 5:00pm local time (1500 GMT) and police promptly intervened to break up the demo, which local authorities had declared illegal.

Officers forcibly removed several dozen activists, who refused to leave the scene, an AFP reporter on the scene saw.

Some chained themselves to railings or lay flat on the ground to make it harder for police to remove them. Officers deployed electric saws to cut through chains.

Protestors watching from a bridge over the road chanted "you are not alone" and "this is what democracy looks like."

On a sunny early autumn afternoon, the demonstrations had initially attracted a peaceful crowd, with some pitching tents on the tarmac and sitting on the road playing cards.

They placed banners reading "turn off the fossil fuel money taps", "people and the climate above profits", and "if we can destroy the world, then we can also save it."

Loudspeakers blared out speeches, slogans, and bursts of music, including "The Final Countdown" by Swedish pop group Europe.

Demonstrators had daubed XR logos and "end fossil fuel subsidies" on the motorway as an elderly group wearing "grandparents for the climate" shirts handed out flyers.

- 'Raising our voices' -

Isabelle, a 25-year-old labour union employee, who refused to give her last name, told AFP: "I think it's essential that we keep raising our voices because this is a cause that matters so much."

"It's an incredibly good atmosphere. People are having fun. There's singing, there's dancing. We're having a good time fighting for our cause."

Many of the activists had conducted a week-long march from Arnhem in the east of the Netherlands that culminated in the protest on the A12 motorway that serves The Hague.

The XR group said some planned to take advantage of the police absence to camp out overnight in the motorway tunnels.

"We will keep coming back until the subsidies are abolished," said XR spokeswoman Rozemarijn van 't Einde, adding that they amounted to between 39.7 and 46.4 billion euros ($44.0-51.4 billion) per year.

The XR group regularly targets the A12 motorway and police often arrest hundreds of protestors.

"The blockade will be the most disruptive since the first blockade on July 6, 2022," said the group.

"The severity of the climate and ecological crisis justifies the additional nuisance."

Dutch Justice Minister David van Weel said police "always act in emergencies, even during work stoppages" so he was not concerned about public safety.

He said it was a "bit ironic" the activists were urging authorities to ensure their safety given they rail against what they call disproportionate and heavy-handed policing.