Charlie Hebdo suspect 'fled to Syria before attack'

France has vowed to combat terrorism with "a cry for freedom" and a giant rally for unity after three days of bloodshed in which a total of 17 people were killed by al-Qaeda-linked attackers.

Paris was due to host the rally on Sunday in response to the Wednesday attack at the Paris offices of the Charlie Hebdo satirical magazine, which killed 12 people, and the deaths of five others at a grocery in northern Paris on Friday as police tracked down and killed the prime suspects.

Police on Saturday said they were searching for Hayat Boumeddiene, a suspected accomplice of grocery store attack Amedy Coulibaly. However, a Turkish intelligence official told the AP news agency on that a woman by the same name who strongly resembled Boumeddiene flew into Istanbul on January 2 and had probably slipped into Syria.

More than 2,000 police are being deployed in Paris on Sunday to protect hundreds of thousands of expected marchers, in addition to tens of thousands already guarding synagogues, mosques, schools and other sites.

The rally "must show the power, the dignity of the French people who will be shouting out of love of freedom and tolerance," said France's prime minister, Manuel Valls.

People... will be shouting out of love of freedom and tolerance. - French prime minister Manuel Valls

"Journalists were killed because they defended freedom. Policemen were killed because they were protecting you. Jews were killed because they were Jewish," he said. "The indignation must be absolute and total - not for three days only, but permanently."

Boumeddiene, 26, reportedly married Coulibaly in an Islamic ceremony in July 2009, a union not recognised under French law.

The French radio network, RTL, released audio on Saturday of Coulibaly, in which he attacks Western military campaigns in Syria and Mali, and describes Osama bin Laden as an inspiration.

Al-Qaeda's branch in Yemen said it directed Wednesday's attack against Hebdo to avenge the honor of the Prophet Muhammad, a frequent target of the magazine's satire. Cherif and Said Kouachi, the Hebdo attackers, were reported to have said that they were working for the Yemen branch as they attacked the office.