France marks a day of mourning for the deaths of 12 people in Wednesday's shooting attack on the Paris offices of a satirical magazine as a manhunt continues for the two main suspects.
Police have issued arrest warrants for the two suspected gunmen, brothers Cherif and Said Kouachi, saying they are armed and dangerous. A third suspect -- 18-year-old Hamyd Mourad -- turned himself in to authorities, but it appears uncertain whether he was involved.
Thousands of police were involved in the manhunt, which was focused on northern France. The French news agency AFP reported that witnesses had apparently spotted the brothers at a petrol station in the northern Aisne region.
Police identified the suspects after one of them left his identity card in the getaway car after Wednesday's killings.
Authorities said they have so far detained seven suspects, mostly acquaintances of the brothers, in relation to Wednesday's deadly attack on the offices of Charlie Hebdo, the weekly magazine known for cartoons that occasionally mock Muslim extremism.
Police in Paris said a policewoman died after being shot Thursday in the southern part of the capital. It was unclear yet whether the shooting was related to the search for the Charlie Hebdo suspects.
Authorities believe the attack was motivated by radical Islam. The older brother, Cherif, served prison time a few years ago for his involvement in a network sending fighters to Iraq.
Interviewed on French radio Thursday morning, Prime Minister Manuel Valls said both suspects were known to intelligence services. He described them acting like soldiers.
Valls also said preventing a second attack is the government's main concern.
Both the Islamic State and al-Qaida have threatened France.
Flags are flying at half-staff on Thursday, schools have been closed and security has been stepped up around the Paris area following the country's deadliest terrorist attack in decades.
President Francois Hollande convened an emergency cabinet meeting, before a moment of silence was held at midday.
Tens of thousands of people poured into the streets of cities across France to show support for the victims.
On Wednesday, tens of thousands of French staged peaceful rallies around the country. Jean-Francois Jouanne grew up with Charlie Hebdo's cartoonists who were among those killed Wednesday.
“I'm here to show support for this wonderful team and to show that we are for the freedom of speech and free expression. Barbarity won't kill the voice of citizens who believe in freedom of speech,” Jouanne said.
Even before the attack, France, home to Europe's biggest Muslim population, was on high alert like many countries that have seen citizens leave to fight alongside the radical Islamic State group in Iraq and Syria.
France has a long history in dealing with terrorism, stretching back to the 1990s when Algerian terrorists staged bombing attacks on Paris subways. More recently, more than 1,000 French nationals have headed to Iraq and Syria to join jihadist movements.
Witnesses to attack
The gunmen burst into the Charlie Hebdo offices Wednesday during an editorial meeting. Witnesses reported hearing the masked gunmen shouting "God is great!" in Arabic as they entered the newsroom, but say they also spoke fluent French.
They were also heard shouting that they had avenged the Prophet Muhammad.
Ten journalists were killed, including editor Stéphane Charbonnier and well-known cartoonists Georges Wolinski, Jean Cabut and Bernard Verlhac, who went by the pen name Tignous. Two police officers also were killed. Eleven people were wounded.
Amateur video recorded near the office shows two men dressed in black rushing at a policeman on the street, and shooting him multiple times as he cries out and raises his hands.
France raised its terrorism alert to the highest level after the attack.
The motive behind the attack remains unclear, but the Wednesday shooting is not the first time Charlie Hebdo has been the target of violence. Its office was firebombed in 2011 after publishing a cartoon of the Prophet Muhammad on its cover.
Shortly before Wednesday's massacre, Charlie Hebdo published a satirical cartoon on social media depicting Islamic State leader Abu Bakr al-Baghdadi as a New Year well-wisher.
U.S. President Barack Obama joined several world leaders in offering condolences and condemning Wednesday's attack.
U.N. Secretary-General Ban Ki-Moon said such violence should be a unifying force. "This horrific attack is meant to divide; we must not fall in to that trap. This is a moment for solidarity around the world, we must stand strong for freedom of expression and tolerance and stand against forces of division and hate," Ban said.
Muslim leaders in France also have denounced the shooting.
Leaders in France and abroad pledged to resist terrorists.
Hollande denounced the shootings as a terrorist attack and said several other terror plots have been foiled in recent weeks.
"We were being threatened because we are a country of freedom. And because we are a country of freedom, we will fight against these threats and we will punish the aggressors," Hollande said.
U.S. Secretary of State John Kerry urged the French not to give in to intimidation.
"Free expression and a free press are core values. They are universal values. Principles that can be attacked but never eradicated because brave and decent people around the world will never give in to the intimidation and the terror that those seeking to destroy those values employ," Kerry said on Wednesday.
Pope Francis described it as a "horrible attack" saying such violence, "whatever the motivation, is abominable, it is never justified."
Meanwhile, cartoonists reacted as they know best, composing biting satirical drawings against what editorialists said was an attack on the foundations of democracy.
Among the cartoons that went viral online was one by Australia's David Pope: a picture of a gunman with a smoking rifle standing over a body, bearing the caption "He drew first."
Christophe Deloire, Head of Reporters Without Borders, called Wednesday a “black day” for the French press.
"How can we imagine a worse attack when this editorial team, Charlie Hebdo, has already been threatened in the past. They've had very serious threats but nothing... there was never anything of this proportion. This attack against Charlie Hebdo is maddening," Deloire said.
Some material for this article came from Reuters and AFP.