Police arrested a dozen people suspected of helping the Islamist militant gunmen in last week's Paris killings, the city prosecutor's office said on Friday as U.S. Secretary of State John Kerry arrived for talks.

The arrests came after Belgian police killed two men who fired on them during one of about a dozen raids on Thursday against an Islamist group and German police said they had arrested two people following a raid on 11 properties linked to radical Salafists.

Centred on southern Paris suburbs including the Montrouge area where a young policewoman was killed in the attacks, the arrests were for suspected "logistical support" for the shootings, an official said.

Seventeen victims and the three attackers died in three days of violence in Paris last week that began with an assault on the offices of satirical weekly Charlie Hebdo.

Paris's Gare de l'Est train station was evacuated at 8:00 a.m. local time (0700 GMT) after an alert but reopened about an hour later, the SNCF state railway said, without giving further details.

Kerry met French Foreign Minister Laurent Fabius early on Friday before greeting President Francois Hollande with a hug in the courtyard of the Elysee presidential palace.

Kerry had said on Thursday that his visit to France was to give a "big hug" to Paris. Senior U.S. officials were absent from a commemoration march held in Paris on Sunday attended by dozens of world leaders. President Barack Obama's administration conceded that was an omission.

"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," Kerry told Hollande on Friday.

Hollande called the shootings France's 9/11 in reference to the Sept. 11, 2001 attacks in New York.

"Together we need to find the right responses and this is the purpose of our meeting here today, beyond the friendship," he said.

Investigators are still poring over the complex chain of events that led to three French nationals - two brothers with Algerian roots and a third of African extraction - perpetrating the worst attacks on French soil for decades.

Belgian investigators said they are trying to establish if a man detained in the city of Charleroi on suspicion of arms trafficking had any links with Amedy Coulibaly, the gunman who killed four Jews at a kosher supermarket in Paris last week.

His lawyer Michel Bouchat told French media the man was not an associate of Coulibaly and had merely sold him a car. The man in question already contacted police on Tuesday to say he had had contacts with Hayat Boumedienne, the partner of Coulibaly now believed to be in Syria.