The Paris prosecutor's office said counter-terrorism investigators are probing Friday morning's incident at the Chatelet station in the centre of the capital, based on preliminary examination of the attacker's background. The man was disarmed and immobilised by the soldier, who was not injured.
The French army's anti-terrorism Operation Sentinel was established following the 2015 terrorist attacks in Paris.
French Defence Minister Florence Parly said the number of troops involved in its Sentinelle operation would remain at 7,000 under the plan.
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On August 9, at least six French soldiers were injured, three of them seriously, when they were hit by a vehicle in a north-western Paris suburb.
Including the attacks today in Paris and Burgundy, France has already seen 10 terrorist incidents in 2017.
Further noting that the soldier who was targeted by the assailant, was a member of Operation Sentinel, a task force that has been assigned to protect prominent sites in the region. One officer was hit in the head with the hammer, prompting police to fire at the attacker. The attacker is believed to not be known to police.
The attacker is said to have approached the soldier from behind before lunging at him with a blade.
France declared a state of emergency following attacks in Paris in November 2015, in which more than 130 people were killed.