A video surfaced Sunday that appears to show Paris attacker Amedy Coulibaly explaining his motives, claiming he and the shooters who attacked the magazine
In the video he pledges allegiance to the militant group, which has seized extensive parts of Iraq and Syria.
"It is vengeance for the prophet" Muhammad, he says in the video, adding, "It is amply deserved for a long time."
The video was released as millions of people joined rallies across France honoring the 17 victims of last week's violence and as police searched for Coulibaly's girlfriend, who may have fled to Syria.
Coulibaly, 32, was killed Friday by police in a raid on a kosher market where he had taken hostages, four of whom he reportedly killed. The attack came a day after Coulibaly allegedly killed a French policewoman and two days after he was believed to have shot and wounded a jogger in the Paris suburbs.
In the video, a man who is identified as Coulibaly and resembles images released by French police speaks in broken Arabic and fluent French about being a "soldier of the caliphate," Islamic State's religious government. He also pledges allegiance to "caliph Ibrahim," a reference to Abu Bakr Baghdadi, the militant group's self-proclaimed leader.
The man, also identified in the video as Abou Bassir AbdAllah al-Ifriqip, claims he coordinated his attack with brothers Cherif and Said Kouachi, who French authorities say carried out the attack at Charlie Hebdo.
The roughly seven-minute video released on militant websites and linked to by SITE Intelligence Group, which monitors online activity by Islamists, could not be independently verified. Two men who knew Coulibaly confirmed his identity in the video to the Associated Press, but asked not to be identified.
Investigators were still attempting to authenticate the video late Sunday.
"We are going to have to determine the conditions in which this video was posted," Bernard Petit, the head of the Paris judicial police, told France's TF1 TV.
French police have already said the attackers belonged to the same terrorist cell. But the man in the video goes further, discussing how and why they coordinated at certain times, but not others.
"My brothers, our team, divided things in two," says the man, speaking in front of an Islamic State flag. "If we did things a bit together and a bit separately it was to have more impact."
Survivors of the shooting at Charlie Hebdo’s offices have said the attackers told them they were from
But in the video, the man identified as Coulibaly says the militants' motive was retribution for French attacks on Islamic State, seen by many analysts as a rival to Al Qaeda.
"If you attack the caliphate and Islamic State, you will be attacked," he says. "France is a legitimate target."
"You bombard there regularly, you invested in forces, you kill civilians, you kill combatants, you kill. Why?" he says, adding: "We are not going to let this happen. We will fight, God willing, until the word of God the great and almighty is supreme."
The man, who speaks calmly and without an apparent script, presents himself as a militant -- wearing body armor, sitting near an array of weapons and at one point even doing push ups -- and urges Muslims in the West to join the cause, saying he saw many able-bodied men in Paris mosques who could "defend" Islam.
"I address my speech to my Muslim brothers everywhere and especially in Western countries," he says. "I ask them: what are you doing?"
It is not immediately clear when the video was filmed, although there are clues in the background and in what the man says. He speaks of attacking the policewoman in the past tense, suggesting the video was filmed after the Thursday shooting.
Early in the video, radio reports of the Wednesday attack play as voice-over, and at the end, there is news footage of the raid on the kosher market.
Some of the comments in the video match those made by Coulibaly and aired on France's BFMTV shortly before the police raid on Friday in which he was fatally shot. In that interview, and comments recorded after he failed to hang up the phone, Coulibaly called his actions revenge for the French military incursion against Islamist militants in the West African nation of Mali, Western intervention in Syria, airstrikes against Islamic State and a French law banning women from publicly wearing head scarves.
"Each time, they try to make you believe that the Muslims are terrorists. But I was born in France. If they hadn't attacked elsewhere, I would not be here," Coulibaly reportedly could be heard telling hostages at the kosher market on Friday.
The video was also initially posted on YouTube on Sunday, but has been taken down.
On Sunday, a Paris prosecutor told the Associated Press that ballistics tests linked the gun used at the kosher market to the jogger's shooting Wednesday in the Paris suburb of Fontenay aux Roses.
Police were still searching Sunday for Coulibaly's girlfriend, Hayat Boumeddiene, 26, after an unnamed Turkish intelligence official told AP that a woman fitting her description flew under her name to Istanbul on Jan. 2 and headed south toward the Syrian border.