The incident, in which several bystanders were hurt, caused miles-long queues of traffic on a sunny public holiday and a Dutch motorcyclist died when he struck a stationary truck near the French port of Dunkirk.

Belgian police had been called at dawn to a lorry park near Ostend by truckers reporting an attempt by smugglers to put migrants into vehicles bound for Britain. Four men in a British-registered car forced their way past police units and raced off.

With the suspects ramming patrol cars trying to head them off at speeds touching 200 kph (125 mph), police opened fire, wounding two of the occupants, a Belgian officer told Reuters.

The pursuit continued, however, to the border 40 km (25 miles) away, and outside Dunkirk the suspects smashed into a vehicle involved in an earlier accident.

Several other people were hurt and all four suspects were rushed to hospital. Their identities were not confirmed. Local French newspaper La Voix du Nord said all were Iraqis who had threatened truckers with knives to make them load the migrants.

Belgian officials believe people-smuggling from France to Britain via Belgium has increased since London and Paris stepped up security around the Channel Tunnel and ports, and France in March closed parts of a Calais migrant camp known as The Jungle.

Eighteen people were arrested for migrant-smuggling near Belgian ports in the first four months of 2016, a judicial source said, compared to 41 in all of last year. In February, Belgium reimposed frontier controls on the French border in an effort to stop migrants and drafted in extra police.