Turkish Foreign Minister Mevlut Cavusoglu said Hayat Boumeddiene had crossed into Syria on January 8, the same day that her partner Amedy Coulibaly is suspected of shooting dead a policewoman outside Paris on the second day of the Paris attacks.
"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.
Turkish television channel Haber Turk later broadcast images of a woman it said was Boumeddiene crossing the Turkish border at passport control at Sabiha Gokcen airport in Istanbul.
Wearing a headscarf, she was accompanied by a bearded, unidentified man in the security footage.
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Cavusoglu said the 26-year-old Boumeddiene, who had married Coulibaly in an Islamic ceremony, stayed at a hotel in the Kadikoy district on the Asian side of Istanbul and was accompanied by another person.
He did not give further details on the identity of the other individual and did not make clear if she had travelled to Syria on her own.
Cavusoglu added that Turkey passed the information to the French authorities "even before they asked for it" as soon as Ankara identified her whereabouts.
"We told them: 'The person you are looking for was here, stayed here and crossed into Syria illegally'," he said.
Interior Minister Efkan Ala also said Turkey did not refuse Boumeddiene entry because French authorities had made no such request and that they hadn't warned Ankara that she was "dangerous."
Western countries have long accused Turkey of not doing enough to stem the flow of jihadists seeking to join IS fighters in neighbouring Syria.
But Ankara insists it has now stepped up border security and has repeatedly said the West also has a responsibility to share intelligence.