The Netherlands’ human rights watchdog has said the right to demonstrate is ‘under severe strain’ after 768 protesters were arrested for taking part in a motorway blockade at the weekend.

The College voor de Rechten van de Mens said the preventive arrest of six activists in dawn raids on Thursday morning was especially concerning. The six were accused of inciting a protest by calling on social media for people to block the A12 on Saturday morning.

They were banned from the A12 approach to The Hague at the time of the protest, organised by climate action group Extinction Rebellion, which was advertised in advance but not authorised by the city council.

A reporter and photographer who were covering the demonstration were also arrested, the Dutch journalists’ union NVJ said.

The watchdog said the right to demonstrate was protected by Article 9 of the constitution and only ‘strictly necessary’ restrictions were allowed, which should be applied in the ‘least intrusive way’.

It said the government should facilitate demonstrations where possible and pointed out that temporarily blocking traffic was recognised by the European Court of Human Rights as a legitimate form of protest.

‘Implementing law enforcement measures such as arrest, interrogation and prosecuting organisers for incitement, before the demonstration has even taken place, is an extremely severe tool,’ it said in a statement.

‘It can have a paralysing effect: other people may be deterred from exercising their right to freedom of expression and peaceful protest. That means we should not be quickly to justify implementing such a measure.’