PARIS -- A knife-wielding assailant tried to attack a soldier in a big Paris subway interchange Friday in an incident being investigated by counterterrorism authorities. The assailant was quickly arrested and no one was hurt.

The Paris prosecutor's office says counterterrorism investigators opened a probe into the incident at the Chatelet station in central Paris, based on preliminary examination of the attacker's background and the method and target of the attack.

Traffic and access at the station, which serves multiple subway and commuter train lines, quickly resumed, though extra security forces were deployed.

The soldier involved was with the Sentinelle force assigned to protect prominent sites after deadly Islamic extremist attacks around France in recent years. Sentinelle soldiers themselves, along with police officers, have been repeatedly targeted.

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Friday's incident came the day after the government announced changes to the Sentinelle force, with a greater focus on temporary and seasonal events. The soldiers will still patrol around major tourist sites, places of worship, train stations and airports.

The attack also comes as police in London, England, search for the culprit or culprits behind a failed bombing attack on a subway train in the Parsons Green neighborhod. While the device appears to have failed to detonate as intended, it still sent a flash of flame ripping through the London Underground train, leaving at least 22 people injured.

Defense Minister Florence Parly said on Europe-1 radio that the attack confirms the government strategy to make the force "more unpredictable ... for potential attackers."