More than a hundred protesters have blocked several routes for migrants, preventing them from gaining access to Calais. The activists’ banners called to “stop the invasion of Europe” and “defend” their city.

The protest was initiated by the Facebook community Génération Identitaire, a group which opposes mass migration. According to the group’s estimates, more than 130 people took part in the rally.

The activists, who were carrying banners with the slogans “Go Home,” “Defend Calais” and “No way,” claimed they had taken control of three bridges leading to the city.

At least 12 protesters have been detained by riot police, the group later wrote.

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“For months, Calais has been a symbol …of the real invasion confronting our continent,” the group wrote on Facebook, saying that the city has recently seen “attacks against police, against motorists and truck drivers, city riots, the total disintegration of social life and the economy.”

The group blamed political leaders in France and across Europe for the deteriorating situation in the city.

READ MORE: Angry Calais residents protest in Paris over migrant crisis (PHOTOS, VIDEOS)

“Since these governments refuse to protect people by restoring the borders,… they will see people building barricades! As this morning in Calais,” the group added.

Numerous photos and videos on social media show the protesters surrounded by police.

The rally comes a day after a huge blaze ripped through the Calais ‘Jungle’ refugee camp. The cause of the fire is still unknown.

On Friday, Xavier Bertrand, president of the Nord-Pas-de-Calais-Picardie region, told the Guardian that France wants UK border guards to tell refugees that Britain is tightening asylum rules.

“What we need now is UK border guards going through the camp at Calais every week telling the people that it is no longer the case that the UK is an El Dorado,” he said.

He added that Calais residents “are exasperated.” “It is not sustainable for the region. I do not want a drama, it’s what I want to avoid, but it’s possible someone will be killed unless we make progress,” he said.

Earlier in March, hundreds of Calais residents arrived in Paris to protest against the deteriorating economic situation in their region, which they say has been caused by the migrant crisis.

130 militants de @G_IDENTITAIRE bloquent les accès à la ville de #Calais pour les clandestins. #NoWay ! pic.twitter.com/GAmjqiACaM — Pierre Larti (@PierreLarti) March 12, 2016

Doctors Without Borders have opened a new migrant camp near the town of Grande Synthe, in the Nord-Pas de Calais region. The camp was set up without the approval of the French government.

À #Calais ou ailleurs : on ne recule plus !@G_IDENTITAIRE défend Calais et ses Calaisiens ! pic.twitter.com/uC7QI0hGU9 — Pierre Larti (@PierreLarti) March 12, 2016

The new camp project was launched after French authorities ordered the demolition of part of the Calais Jungle camp, which served as a temporary home for over 5,000 asylum seekers. It was the largest makeshift camp in Europe and has gradually turned into a small town with its own social life.

On ne partira pas tant que #Calais ne sera pas protégé ! #Junglepic.twitter.com/y1iFMGmeyw — Damien Rieu (@DamienRieu) March 12, 2016

In February, a court in Lille authorized the demolition of the Jungle, but commanded police to spare public facilities such as mosques, restaurants and schools that have sprung up on the site.

Most Jungle residents, whose overall numbers likely exceed 4,000, are from the Middle East, Africa, and Afghanistan. Most have traveled to France in the hope of crossing the English Channel to the UK, after having had their applications rejected elsewhere, or in expectation of better prospects in the country.