The Netherlands is taking extra ‘visible and invisible’ security measures following the terrorist attacks in France, prime minister Mark Rutte said on Friday.

The ongoing events in Paris ’emphasise the need to remain alert,’ the prime minister told reporters after the weekly cabinet meeting.

People who ‘notice things’ which could point to preparations for a terrorist attack must make them known, he said. He also urged everyone who is aware of someone planning to travel to Syria to come forward.

In the meantime, the Dutch should ‘continue to live as we are accustomed to, in openness and diversity’.

Rutte said he had been extremely moved by Thursday night’s gatherings in support of French satirical magazine Charlie Hebdo which took place all over the country. Such public declarations of solidarity are the best possible answer to such a ‘terrible, barbaric attack’, the prime minister said.

The terrorist threat in the Netherlands remains ‘substantial’, the second highest level.

Meanwhile, security minister Ivo Opstelten has confirmed around 180 Dutch jihadis have travelled to Syria and Iraq, of whom 35 have returned. They are all being monitored either by the police or security officials.

So far at least 21 Dutch nationals have been killed while fighting with Islamic militants.