Around 50 French masked alt-left extremists surrounded the bus of Catholic pro-life demonstrators who were heading to a March for Life event in Paris and attempted to set several of the bus occupants on fire.

The attack occurred in the city of Rennes in Northwest France at around 7:45 am on Sunday and saw the bus, which was rented by a Catholic association, surrounded by masked extremists, Le Télégramme reports.

One of the pro-life demonstrators described the attack, saying: “We were waiting for the bus. When it arrived we boarded and the bus was surrounded by about fifty demonstrators, obviously, they knew we were going to embark there.”

The far-left extremists formed a human wall around the vehicle and then, according to witnesses, one of them threw a burning smoke bomb in the bus itself. The smoke bomb hit the window and landed on a man whose coat was burned by the bomb along with another woman whose sweater was also burned.

After only 15 seconds or so, the passengers were able to get the smoke bomb out of the bus with one passenger complaining about breathing problems and was forced to go outside.

Thirty minutes after the extremists surrounded the bus, the police arrived on the scene but were not able to move the activists until 10:30, almost three hours after the blockade had begun.

Thousands of far left activists protested incoming French President Emmanuel Macron in Parishttps://t.co/M0zOa4TFAJ — Breitbart London (@BreitbartLondon) May 8, 2017

Far-left violence is commonly seen against police in France and is most common in Paris. Last year, during the French presidential elections, far-left Antifa extremists fought with police and used Molotov cocktails to set one officer on fire.

The far-left in France have also been linked to attacks on other right-wing activist groups like the hipster-right anti-mass migration Generation Identitaire.

In November, 14 Antifa extremists were arrested plotting to attack an Identitarian event, although several German media outlets falsely reported that members of Generation Identitaire were arrested. After several days, Der Spiegel and others corrected their reporting.