26-year-old partner of gunman Amedy Coulibaly, who learned to use weapons with radicals in France, could now be in Syria

A slight, 26-year-old woman, skilled at shooting crossbows and probably armed with assault rifles, is the most hunted and feared person in France, but may now be beyond reach of its security forces.

Hayat Boumeddiene stares out sleepy-eyed from a police “wanted” poster that was issued before Amedy Coulibaly, her husband under Islamic law, launched a murderous rampage in a Jewish supermarket in Paris.

But officials now believe she was in Syria by the time that image was published, taking a flight to Istanbul last week and then crossing the border on foot, French media reported.

Police shot Coulibaly dead after a five-hour siege on Friday, and separately killed two brothers, Chérif and Saïd Kouachi, members of the same extremist cell.

The group had launched three days of terror by gunning down cartoonists, staff and policemen at the offices of the Charlie Hebdo satirical magazine on Wednesday and killing a policewoman on Thursday before Friday’s bloody hostage standoffs with police.

Boumeddiene is now the only known survivor from the group of four who planned the crimes that killed 17 people. French security forces are desperately searching for Boumeddiene, who they fear could unleash more carnage on the shattered country.

Security forces recorded more than 500 calls last year between her and the wife of Chérif Kouachi. “We can call this complicity by furnishing of means. We must interrogate her so she explains exactly if she did this under influence, if she did it by ideology, if she did it to aid and abet,” Police Union spokesman Christophe Crepin told the Associated Press on Saturday.

“You must consider her as the companion of a dangerous terrorist who needs to be questioned. If she doesn’t come [to us], she will be found.

One of seven children, Boumeddiene lost her mother as a young child. Her father, who worked as a delivery driver, struggled to cope with raising his large family alone, and she was taken into foster care when she was aged about eight or nine.

In 2009 she married Coulibaly in an Islamic ceremony. Her new husband was the only boy in a family of 10 and, in his mid-20s, was unemployed and already shadowed by a criminal record and ties to extremist groups.

As is common in conservative Islamic practice, she was not present in the room when the marriage certificate was signed by her father and new husband.

They did not hold a civil ceremony, so their union is not recognised by French law, but there seems no question they considered themselves a married couple, and they lived together in a flat in Bagneux, a Paris suburb.

Once married, Boumeddiene became one of the very few women in France to wear the niqab, a full-face veil that leaves only the eyes uncovered. The decision apparently cost her a job as a supermarket cashier, Le Parisien reported.

Personally close to Islamic radicals known to French internal security services, she joined her husband on a trip to meet Djamel Beghal, a radical preacher under house arrest in southern France. On that trip, they apparently practised shooting with crossbows; photos show her in a niqab, aiming at the camera and out of shot.

Boumeddiene was once interrogated by French officials about her reaction to terrorist acts committed by al-Qaida, French judicial records obtained by the Associated Press show. “I don’t have any opinion,” she answered, but immediately added that innocent people were being killed by the Americans and needed to be defended, and that information provided by the media was suspect.

Still, she had doubts about her own husband’s religious faith, according to a police interview obtained by Le Monde.

“Amedy isn’t really very religious. He likes having fun,” she told police. Other pictures show her in a bikini, nestling up to him on a beach holiday.

She waited for Coulibaly during his four-year jail sentence for armed robbery, and he moved back in with her after he was released last year. He was probably already planning last week’s attack with the Kouachi brothers, after meeting one of them in jail.

His own spree of violence began the day after the Charlie Hebdo attack, with the fatal shooting of a female police officer, Clarissa Jean-Philippe, in Montrouge. The next day, around lunchtime Coulibaly stormed into a Jewish supermarket in northern Paris, carrying two Kalashnikov assault rifles, killing four shoppers.

He then took at least 15 people hostage in an ordeal that dragged on until the early evening, when heavily armed elite forces stormed the building and shot him down. The full horror of the stand-off only began to emerge on Saturday.

One relatively fortunate group of six were hidden in a basement cold storage room by a Muslim shop attendant called Lassana Bathily, who risked his own life to save theirs.

“When they came running down I opened the door of the fridge. Several came in with me. I turned off the light and the fridge … I closed the door and I said “you stay quiet there, I’m going back out,” she told French station BFM TV.

Another group were less fortunate, trying to take shelter in a second cold room where the door did not lock, a survivor who identified himself as Mickael B said. The gunman ordered them back upstairs. “I am Amedy Coulibaly, Malian and Muslim. I belong to the Islamic State,” he told the group.

One of them was shot down soon after when he tried to grab one of Coulibaly’s guns to turn it on the attacker, but found it jammed and was killed for his courage. “[Coulibaly] fired on the person who did it and he died instantly,” Mickael said.

Mobile phones proved key to the police’s successful simultaneous raids on the supermarket and a printing company where the Kouachi brothers were holed up, as hidden hostages phoned in with tactical information.

Coulibaly also handed the police an intelligence advantage, when he called a journalist to broadcast a message, but forgot to hang up the phone after speaking, allowing police to listen in on his movements, the AFP agency reported. He said he targeted the shop “because it was Jewish”, and handed down a list of demands.

“They must stop attacking the Islamic State, stop unveiling our women, stop putting our brothers in prison for nothing at all. It is you who is financing [the government]. You pay taxes,” he said. When a hostage said that paying taxes was a legal obligation, Coulibaly responded. “You do not have to. I do not pay taxes.”

At the print works in Dammartin-en-Goele, the Kouachi brothers took the manager hostage but allowed him to leave after he patched up a neck wound on Saïd, the older of the two. Relief at his escape was overshadowed by worries about a young graphic designer who had managed to stay hidden “under a sink in the canteen”, feeding the police information, Paris prosecutor François Molins said.

Younger brother Chérif also called BFM TV during the siege. In a calm, assured voice, the gunman could be heard saying he had been sent by al-Qaida Yemen.

Kouachi was “really prepared”, journalist Igor Sahiri told the BBC. He said: “It was somebody very serene. He was very calm. It was just like a normal discussion, no rudeness. My feeling was that this kind of man is ready to die.”

Overnight, al-Qaida in the Arabian Peninsula’s top sharia official, Harith al-Nadhari, threatened France with further attacks, the SITE monitoring group reported.

“It is better for you to stop your aggression against the Muslims, so perhaps you will live safely,” he said.

“If you refuse but to wage war, then wait for the glad tiding.”