Services from Port of Calais have been disrupted after 50 migrants got on to ship, the city’s mayor Natacha Bouchart has said.
It is understood that about 50 migrants in Calais boarded a PO ferry named the Spirit of Britain while it was unloading.
Ferry company DFDS Seaways tweeted that the port had been closed due to a “migrant invasion”.
Police have been called and are at the scene.
PO Ferries described it as a “security incident” and said passengers could expect to a delay of between 90 and 120 minutes.
The incident followed a demonstration in favour of migrants, which according to AP news agency, attracted a crowd of 2,000 people.
Some of the protesters at the demonstration carried banners saying “refugees welcome here”.
Thousands of migrants are currently living in camps known as “the Jungle” on the edge of Calais,
In August last year, the UK and France signed an agreement on new measures to try and alleviate the crisis, including a new command centre to help tackle the trafficking gangs.
Meanwhile, Jeremy Corbyn has visited a migrant camp in northern France and spoken of the “dreadful conditions” there.
The Labour leader said conditions in the Grande-Synthe camp near Dunkirk would be a “disgrace anywhere”, and Britain should be “part of bringing European support to people”.
The situation in Calais is part of a wider migration crisis in Europe – caused largely by people fleeing war and oppression in countries such as Syria, Afghanistan and Eritrea.