French authorities have detained 12 people overnight in the suburbs of Paris, the prosecutors office has said, in connection with the last week's attacks in the city that left 17 people dead, including 12 at the office of satirical newspaper Charlie Hebdo.

The detained were to be questioned about "possible logistic support" they may have given to the gunmen, in particular weapons and vehicles, AFP news agency reported on Friday.

Raids were still taking place in Montrouge just outside Paris, where gunman Amedy Coulibaly killed a policewoman last week, Grigny where he grew up, Fleury-Merogis south of the French capital and Epinay-sur-Seine north of the city.

Paris police evacuated the Gare de l'Est train station on Friday after a bomb threat, as authorities across Europe pressed on with efforts to prevent new violence after one of the worst attacks in decades. Similar anti-terrorism raids and arrests took place in Belgium and Germany.

According to an AFP police source, investigators have followed several people over the past few days that had been pinpointed thanks to probes on people in the alleged entourage of the Kouachi brothers, who waged the Charlie Hebdo attack, and Coulibaly, who killed a policewoman and four people in a kosher supermarket.

Among other things, they are looking for the car of Hayat Boumeddiene, Coulibaly's wanted partner who is now believed to be in Syria.

Earlier this week, France's parliament voted to extend airstrikes against armed group Islamic State of Iraq and Levant (ISIL).

Meanwhile, US Secretary of State John Kerry arrived in France to meet top officials to express the United States' solidarity with the French people. 

"I think you know that you have the full and heartfelt condolences of the American people and I know you know that we share the pain and the horror of everything that you went through,'' said Kerry, who had said he was coming "to share a big hug with Paris", as he greeted French President Francois Hollande.

Source: Agencies