Paris: Elite French security forces tightened the net today on two brothers suspected of slaughtering 12 people in an Islamist attack after discovering an abandoned getaway car in a northeastern town.
Helicopters buzzed overhead as police mounted a frantic manhunt for the two fugitives thought to be behind the bloodbath at Charlie Hebdo magazine in Paris, the worst terrorist attack in France for half a century.
Earlier they had been identified -- reportedly masked and armed -- at a petrol station near the town of Villers- Cotterets, 80 kilometres from the French capital, before fleeing again.
An AFP reporter saw 20 heavily armed security force officers surround a nearby house and storm it, keeping journalists away from the scene.
Islamic State, the militant group sowing terror across swathes of Iraq and Syria and calling for global jihad, hailed the brothers as "heroes" on its Al-Bayan radio station.
This was the first reaction by the jihadists to yesterday's massacre in which the fugitive brothers allegedly said they were taking revenge for Charlie Hebdo's repeated publication of cartoons seen by many Muslims as sacrilegious.
In a further sign of the attackers' motives, a source close to the case said that Molotov cocktails and jihadist-style flags had been discovered in another getaway vehicle used by the attackers.
A maximum security alert declared in the capital yesterday was expanded to the region where today's manhunt took place.
Arrest warrants were issued for Cherif Kouachi, 32, a known jihadist convicted in 2008 for involvement in a network sending fighters to Iraq, and his 34-year-old brother Said. Both were born in Paris and are French nationals of Algerian origin.
The two men were likely to be "armed and dangerous", authorities warned.
Interior Minister Bernard Cazeneuve said seven other people had been detained in the hunt for the brothers.
Prime Minister Manuel Valls, meanwhile, told French radio the two suspects were known to intelligence services and were "no doubt" being tracked before yesterday's attack.
Meanwhile, several other incidents rocked the jittery nation, although it was not clear whether they were linked to yesterday's attack.
Just south of Paris, a man shot dead a policewoman and wounded a city employee with an automatic rifle -- an act that prosecutors said they were treating as terrorism.
There was an explosion at a kebab shop in eastern France, with no casualties immediately reported. And two Muslim places of worship were also fired at in the wake of yesterday's attacks, prosecutors said.
In their hunt for the attackers, police were using forensic evidence and an ID card found in a car abandoned by the gunmen after the attack.
Mourad Hamyd, an 18-year-old suspected of being an accomplice in the attack, handed himself in after he saw his name "circulating on social media", police sources said.
It was not clear what role, if any, he played in the attack.
As the dramatic chase unfolded, bells tolled across France at midday, public transport paused and people gathered outside the headquarters of Charlie Hebdo in pouring rain with banners reading "Je Suis Charlie" (I am Charlie).
Across the world, crowds also gathered from Moscow to Washington under the banner "I am Charlie" to show support for the controversial magazine.
Declaring a national day of mourning today -- only the fifth in the last 50 years -- President Francois Hollande called the Charlie Hebdo bloodbath "an act of exceptional barbarity". The Eiffel Tower in Paris was to dim its lights at 8:00 pm (local time).
The government also called for large demonstrations to show solidarity across the country on Sunday.
National television ran constant live coverage of the manhunt for the masked, black-clad gunmen, who killed some of France's most outspoken journalists, as well as two policemen.
Hollande ordered flags to fly at half-mast for three days in France and convened an emergency cabinet meeting.
"Nothing can divide us, nothing should separate us. Freedom will always be stronger than barbarity," said the president, calling for "national unity".
As a sign of this unity, Hollande invited arch-rival and opposition leader Nicolas Sarkozy to the Elysee Palace, his first visit since losing power in 2012.
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's main Islamic groups urged Muslims across the country to observe today's minute of silence and for imams to condemn terrorism.
But Parisians battled to come to terms with the violence.
Herve Roch, father of two children aged nine and four, said: "You have to explain what happened (to the children). We told them that evil people came to do bad things and the police would catch them."
"I'm an old woman. I lived through the occupation. France needs to wake up so we still have freedom of thought," said Monique Valton, 81.
US President Barack Obama led the global condemnation of what he called a "cowardly, evil" assault.