Up to three gunmen entered the Primark store in Villeneuve-la-Garenne at 6.30am local time, sources said.
According to Le Figaro, quoting a police source, a Primark employee sent a text message to a friend at 7am saying he was being held hostage by two armed men.
"Around 6:30 am (0530 GMT), two or three armed criminals went into the Primark store for what we think was initially an attempt at armed robbery," a police source, who wished to remain anonymous, said.
The source confirmed 10 staff were unaccounted for but could not confirm the reports that they had been taken hostage.
Le Parisien newspaper said that up to 18 hostages had been held.
It is understood all have been released but the gunmen are at large.
The paper quoted witnesses who said people ran near the store screaming: "They are armed, they are armed."
A Primark spokesman said: "We can confirm that there has been an incident at our Quartz shopping centre store in northern Paris.
"Police are in attendance and media inquiries are being referred to them.
"We will do all we can to support our staff and their families. We hope for a speedy and safe end to this incident."
