Lorry drivers and farmers are blockading the main motorway route into Calais in a protest calling for the closure of the town's migrant camp.
Local traders and trade unions are also taking part and cross-Channel travellers are facing disruption.
But the Port of Calais says a diversion has been put in place and ferries are operating as normal.
Two convoys of trucks left Dunkirk and Boulogne on the A16 motorway towards Calais on a "go slow".
Farmers in tractors waited on the side of the road to join the convoy.
Meanwhile, in Calais hundreds of protesters carrying banners gathered on the motorway, which is located close to the entrance to the Channel Tunnel and ferry terminals.
Channel Tunnel operator EuroTunnel advised motorists in France heading to Calais to follow one of its suggested alternative routes, but says its services are operating to schedule.
P&O Ferries and DFDS Seaways say travellers who are delayed will be put on their next available sailings at no extra cost.
The presence of the camp, say the organisers of the protest, is undermining Calais.
The lorry drivers say they have seen increasing threats from organised gangs and migrants, who have been attempting to board vehicles to reach the UK.
Farmers are said to be angry at the destruction of crops caused by the swelling of the migrant camp known as the "Jungle".
The camp has become the focal point of France's migrant crisis, with about 7,000 people, mainly from the Middle East, Afghanistan and Africa, living there.
BBC News correspondent Richard Galpin says one asylum seeker from Sudan has said he is saddened by the way local people view the camp, saying all they want is to live in peace after escaping from conflict.
In recent weeks there have been reports of criminal gangs adopting new techniques to try to get migrants into the UK.
The Mail on Sunday said a log was thrown at a car carrying its journalists last week in a deliberate attempt to make them crash, to try to divert attention away from migrants boarding vehicles.
And last month the BBC broadcast footage of suspected people smugglers blocking the main route to Calais with a felled tree and threatening motorists with violence.
'Change of tactics'
Jean-Pierre Devigne from France's largest trucking union, the FNTR, told BBC Radio 4's Today programme the protesters were "determined to show to the people we are not happy with the situation" and wanted the camp to be closed.
On Thursday, Mayor of Calais Natacha Bouchart said the blockade would cause "chaos" for British travellers.
Richard Burnett, chief executive of the Road Haulage Association (RHA), said traffic crossing from the UK would find it "almost impossible" to leave the port without access to the A16.
Speaking on Today, Mr Burnett said: "We are very concerned about the impact and as we saw last year... the chances are, if this blockade actually backs the port up, then it will strangle the port and we will see implications back on British soil as well."
He said there were "insufficient resources" in place to protect British lorry drivers but he sympathised with the protesters and agreed there needed to be "demonstrable plan" that shows the camp will be dismantled.
In February authorities demolished a large area of the southern part of the Jungle, in an attempt to reduce numbers, but the size of the camp has been steadily increasing, according to estimates, and now protesters are calling for the northern area to be dismantled.
French Interior Minister Bernard Cazeneuve said on Sunday that the government still intended to shut the camp.
But the president of the Association of Calais Traders was quoted in a number of papers as saying: "We are changing our tactics after using soft methods and obtaining nothing but promises from the state that it is giving priority to the wellbeing of the migrants over those of traders, port workers, hauliers, tourists and farmers.
"We will not budge from the motorway until the state gives us the dates for the total demolition of the northern zone of the Jungle."
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