"The perpetrator was waiting for the soldiers to leave the barracks and head to their vehicle", he added. The driver is on the run.
Six soldiers were injured, two seriously, after being hit by a vehicle Wednesday outside their barracks in a suburb northwest of Paris. Police have closed off the roads.
He was detained on a motorway north of the city, but officials said it was too early to say whether he was the man they were looking for.
The attacker was waiting in the dark-coloured vehicle in an alleyway before he drove at speed at the troops as they left their barracks to go on patrol at around 8am local time.
Patrick Balkany, the mayor of the suburb Levallois-Perret, told French news that a BMW was "pre-positioned" on a small side street, with the driver laying in wait for troops to exit the building. It is believed to be a premeditated attack, since the suspect deliberately rammed a vehicle into the group while going at a high rate of speed. It was reported as the group of six soldiers came out of the building to start their shift that the attacker drove into them.
French authorities have since opened a counter-terrorism investigation, after the man said he meant to attack a soldier.
The anti-terror troops are from Opération Sentinelle, set up in the aftermath of the French terror attacks.
Two people were seriously injured and four others were less badly hurt, a spokesman said.
The anti-terrorism unit of the Paris prosecutors' office has launched a probe into the car-ramming, AFP reported, citing a statement from Paris prosecutors.
Minister of the Interior Gerard Collomb said the attack was a "deliberate act".
The incident is the latest in a series targeting security forces in France guarding sites after a string of deadly attacks.
In June a man was shot by police after he attacked an officer with a hammer at the Notre-Dame.
In April, a policeman was shot dead on the Champs-Elysees by a man with a long criminal record, who investigators determined was acting from terrorist motives.