Police in the northern Belgian city of Antwerp said on Thursday they had detained a man who tried to enter the main pedestrianised shopping street in a car at high speed, adding security in the city would be stepped up.

"At about 11 am this morning a vehicle entered De Meir at high speed due to which pedestrians had to jump away," a police spokesman told a news conference, referring to the street name.

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The Belgian prosecutor's office said a 39 year old French national had been arrested and that police found knives, a shotgun and a gas can with an unknown liquid in the car.

The office said "because of these elements, and the events in London yesterday, the case is being taken on by the federal prosecutor's office," which usually deals with extremist attacks.

Additional police and military personnel, including a bomb squad, have been deployed to the centre of Antwerp and security stepped up at the city's port.

Prime Minister Charles Michel said: "we remain vigilant. Our security services have done excellent work."

The events come a day after the nation held remembrance services for the Brussels attacks, which killed 32 people on March 22, 2016.