In the latest ramming incident in Europe, a man drove on Monday his explosives-laden vehicle into a police van that was headed down the famed Champs Elysees avenue in the French capital Paris.

The attacker died in the incident. No police officers or passers-by were hurt in the attack.

The Paris prosecutor’s counter-terrorism unit said it had opened an investigation.

It was unclear how the man, who was not named, had died. Two police officials told The Associated Press that a handgun was found on the driver, who they said was badly burned after the vehicle exploded. They identified him as a 31-year-old man from the Paris suburb of Argenteuil who had an “S” file, meaning he was flagged for links to extremism.

Interior Minister Gerard Collomb said the car had been carrying weapons and explosives. “This once again shows that the threat level in France is extremely high,” Collomb told journalists near the scene.

Four family members of the perpetrator were later put in custody.

The Paris prosecutor’s office said Tuesday that the four were detained overnight in the anti-terrorism investigation into Monday’s attack.

France has been on high security alert following a series of militant Islamist attacks, including the shooting of a policeman in an Islamic State-claimed attack on a police bus on the Champs Elysees, one of the world’s most famous thoroughfares, in April.

Eighty-six people died in a truck attack on a crowd in Nice last year and similar incidents have occurred in other European cities.

The incident in Paris came hours after a van plowed into Muslim worshippers near a mosque in London, injuring 10 people.

In the Paris incident, eyewitnesses saw the man being pulled from the car as it burned, and footage on the Daily Mail web site later showed an officer stripping clothes from the body.

The car struck the front of the van as it overtook a convoy of police vehicles, a police spokeswoman said. Footage recorded shortly afterwards at the site, a short walk from the Elysee presidential palace and the US embassy, showed yellow smoke billowing from the car.

“We saw big flames coming out of the front windows of the car,” 16-year-old eyewitness Adrien Cairo told Reuters.

“Then suddenly we saw four policemen arrive, they knocked on the window, they said ‘Sir, are you alright? Can you hear us?’

He said police broke the window and pulled the man from the car while other police used fire extinguishers to put out the blaze.