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.
The Belgian prosecutor's office said a 39 year old man had been arrested and that police found knives, a shotgun and a gas can with an unknown liquid in the car.
The suspect was named as Mohamed R., a 39-year-old French national of North African origin and living in France.
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.
French authorities later said the suspect was Tunisian national who was probably drunk and trying to escape a police check.
"He did not want to drive into the soldiers. We think he wanted to escape a check," a source close to the case told Reuters.
The suspect was unknown to intelligence services, but known to police for common law crimes, he added.
Francois Hollande , the president of France, said the incident was another reason to maintain a high level of vigilance against possible attacks.
"It seemed to involve a French national, with possibly a certain number of weapons in his boot - it's up to the judges to make a statement on that - who was looking to kill or at the very least create a dramatic incident," Mr Hollande told reporters.
"Therefore we must continue to be on high alert and mobilise all our forces," he added.
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.