A gunman who took at least two people hostage at a post office near Paris, a week after the deadly Islamist attacks in the city, has surrendered to police.

No one was injured in the hostage crisis in Colombes, on the northwestern outskirts of the French capital, authorities said.

Police said early indications suggested the incident was unrelated to the terror attacks that left 20 people dead last week.

The hostage-taker was a customer who seemed "to have lost his head," Paris police told AFP as the crisis was unfolding.

Authorities said the man, who is in his thirties and has a history of mental health problems, cited "a love disappointment" during negotiations. He was reportedly armed with a rifle.

Local resident Dario Spagnolo tweeted a video from the scene:

Early reports suggested the incident might have been a robbery gone wrong, as the gunman was known to police as petty criminal.

He initially claimed to be armed with grenades and a Kalashnikov, Le Parisien reported.

The area was cordoned off by security forces, with a police helicopter hovering over the scene. After a couple of hours, the hostage taker put an end to the standoff, surrendering to police.

The incident came amid high tensions in France, following the three days of terror that engulfed the capital last week.

Paris is at its highest terrorism alert level and anxiety in France has grown as the hunt continues for potential accomplices of the Paris gunmen.

Earlier, Paris Gare de l'Est train station was evacuated after a bomb threat as 12 arrests were made in connection with the Charlie Hebdo massacre and the kosher grocery siege.

Brothers Said and Cherif Kouachi killed 12 people at the offices of satirical magazine Charlie Hebdo before taking a man hostage at a printing warehouse in Dammartin-en-Goële.

Meanwhile, gunman Amedy Coulibaly shot a policewoman dead and then stormed a kosher supermarket killing four Jewish shoppers.

All three attackers were killed by police at the end of two separate tense hostage stand-offs.