France is mobilising 10,000 troops to boost security, as security forces search for what the French prime minister called a "probable" accomplice to three days of bloodshed in and around Paris.

After a crisis meeting on Monday, Manuel Valls said the search is urgent because "the threat is still present" after the attacks that left 17 people dead - journalists at the satirical newspaper Charlie Hebdo, hostages at a kosher supermarket and three police officers.

All three attackers died on Friday in nearly simultaneous raids by security forces.

Video emerged on Sunday of one of the attackers explaining how the raids would unfold and police want to find the person who shot and posted the video.

Valls told BFM television on Monday that France is at war against "terrorism, against jihadism, against radical Islam".

France will deploy nearly 5,000 security forces and police to protect the 700 Jewish schools in the country, Vall said.

Jean-Yves Le Drian, French defence minister, said the total number of deployed forces at high-risk areas across the country will reach 10,000.

Hunt for female suspect

In the days after the attacks, police launched a search operation to track down Hayat Boumedienne, the partner of her partner Amedy Coulibaly, one of the attackers.

Since then, it has been revealed that she was probably not in France at the time of the attacks.

Millions march in France unity rallies

Turkey's foreign minister said on Monday that  Boumedienne crossed into Syria from Turkey on January 8.

Mevlut Cavusoglu told the state-run Anadolu Agency on Monday that she arrived in Turkey from Madrid on January 2, before the attacks, and stayed at a hotel in Istanbul.

"She entered Turkey on January 2 from Madrid. There are images of her at the airport," Cavusoglu was quoted as saying by state-run news agency Anatolia.

"Then she crossed into Syria on January 8. This is clear from the telephone records."

He said Turkish authorities established that she had crossed into Syria on Thursday.

Thursday was also the day Coulibaly shot a policewoman to death on the outskirts of Paris, and a day after the Charlie Hebdo attack.

In France on Sunday an estimated 3.7 million people joined by dozens of world leaders marched in honour of the 17 people killed in the attacks. 

Up to 1.6 million took part in the rally in Paris, among them family members of the 12 people killed in the Charlie Hebdo attack.

Source: Agencies