Two undated handout pictures released by French Police in Paris early Jan 8, 2015 show Cherif Kouachi, 32, (L) and his brother Said Kouachi, 34, suspected in connection with the shooting attack at the satirical French magazine Charlie Hebdo headquarters in Paris, France. [Photo/IC]

PARIS - One man sought in the deadly shooting at a French satirical paper has turned himself in, and police hunted Thursday for two heavily armed men with possible links to al-Qaida in the military-style, methodical killing of 12 people at the office of a satirical newspaper that caricatured the Prophet Muhammad.

President Francois Hollande, visiting the scene of France's deadliest such attack in more than half a century, called the assault on the weekly newspaper Charlie Hebdo "an act of exceptional barbarism."

France raised its terror alert system to the maximum - Attack Alert - and bolstered security with more than 800 extra soldiers to guard media offices, places of worship, transport and other sensitive areas. Fears had been running high in France and elsewhere in Europe that jihadis trained in warfare abroad would stage attacks at home.

French brothers Said and Cherif Kouachi, in their early 30s, should be considered armed and dangerous, according to a police bulletin released early Thursday. Mourad Hamyd, 18, surrendered at a police station in Charleville-Mezieres, a small town in France's eastern Champagne region, said Paris prosecutor's spokeswoman Agnes Thibault-Lecuivre. She did not offer details on Hamyd's relationship to the men, but said he turned himself in because he heard his name on the news in connection with the attack.

By then, heavily armed police had already moved into the nearby city of Reims, searching for the suspects without success. Video from BFM-TV showed police dressed in white apparently taking samples inside an apartment. It was not immediately clear who lived there.

One police official, speaking on condition of anonymity because the investigation was ongoing, said they were linked to a Yemeni terrorist network, and Cedric Le Bechec, a witness who encountered the escaping gunmen, quoted the attackers as saying: "You can tell the media that it's al-Qaida in Yemen."

Cherif Kouachi, who is now 32, was sentenced to 18 months in prison after being convicted of terrorism charges in 2008 for helping funnel fighters to Iraq's insurgency. He said he was outraged at the torture of Iraqi inmates at the US prison at Abu Ghraib near Baghdad.