Some 150 migrants have broken into the port of Calais in northern France, with around 50 of them boarding the front deck of a British ferry. The port had to put its operations on hold until police restored order, arresting three dozen instigators.

“A demonstration in Calais has drawn around 2,000 people and in the end around 200 people entered the port, with approximately 50 of them boarding a ferry, the 'Spirit of Britain', on an external deck,” deputy Calais prefect Denis Gaudin told Reuters.

The Port of Calais has been temporarily closed due to a migrant invasion, as soon as they are cleared the Port will re-open — DFDS Seaways Updates (@DFDSUKUpdates) January 23, 2016

The Spirit of Britain vessel belongs to P&O Ferries which was forced to temporarily halt operations and issue a warning about delays to the service. Migrants reportedly only managed to board the upper decks of the boat as the staff managed to block all the doors.

While some of the migrants eventually agreed to leave the vehicle voluntarily, others were forcefully removed by police who were deployed to restore order. At least 24 migrants were detained, local media reported.

In addition, police detained at least 11 members of the No Borders activist group, which was supporting the Saturday rally in Calais.

“Port of Calais security incident is now resolved. Vessels are now loading and hope to clear backlog as soon as possible,” the ferry company confirmed in a statement.

The incident followed a pro-refugee rally organized by French leftists which gathered about 2,000 people. The activists carried banners reading “refugees welcome here” and said that an increased security presence in the Calais region is a threat to migrants’ lives.

However, many locals were “really frustrated” to see a crowd of activists and migrants walk through their neighborhoods, photojournalist Frederik Sadones told RT. While police were “all around” the place, they did not intervene until something extraordinary happened.

“When the refugees were passing through the city center there were all kinds of reactions … when they were passing a certain house there was a man shouting at them, and they did not like this. So some sort of confrontation occurred,” Sadones said.

Local resident points shotgun at refugees marching through #Calais. No shots fired, nobody hurt. #JungleDeCalaispic.twitter.com/x0Hp6hx4Ad — Frederik Sadones (@FrederikSadones) January 23, 2016

“The man went back inside and he took his hunting rifle back out and he pointed it at refugees … the people quickly dissipated, police showed up as well, but fortunately nobody got hurt and no shots were fired,” he said. “There were a lot of negative reactions from the locals, and this confrontation was the highlight of that.”

The demonstration came as British Labour leader Jeremy Corbyn visited the Calais Jungle and Grande-Synthe (Dunkirk) refugee camps. The British politician expressed his concern with living conditions in the refugee camps and said that the refugee crisis is caused by wars and conflicts.

“What I'm trying to achieve here is to understand the nature of the refugee crisis that's facing the whole of Europe. Ultimately we deal with the situation by dealing with the problem at its source, which are the wars and conflicts,” Corbyn said as cited by the Independent.

“We have got people here who have been here for months, if not longer than that, with no proper education, no access to doctors, no access to dentists, limited access to food - in very cold, very wet conditions. These conditions are a disgrace anywhere. We as human beings have to reach out to fellow human beings,” he added.

READ MORE: RT journalist attacked by knife-wielding gang in Calais

The refugee camp known as “Jungle” was established in Calais last year. Up to six thousand migrants and refugees live in the camp for months at a time, hoping to cross the English Channel to seek asylum in Great Britain which seems for them a better place to start new life than France.

The UK, however, is not so eager to accept their many attempt to cross the channel illegally – primarily through the Eurotunnel. Since the eruption of the migrant crisis in Calais in June, dozens have died in or near the tunnel.

French officials have recently started to demolish a part of the refugee camp to create a “buffer zone” between the Jungle and the highway in order to protect thousands of lorries from migrants.