The youngest of three French nationals being sought by police for a suspected Islamist militant attack that killed 12 people at a satirical magazine on Wednesday turned himself into police, Reuters reported.

The hooded attackers stormed the Paris offices of Charlie Hebdo, a weekly known for lampooning Islam and other religions, in the most deadly militant attack on French soil in decades.

This combo shows handout photos released by French Police in Paris early on January 8, 2015 of suspects Cherif Kouachi (L), aged 32, and his brother Said Kouachi (R), aged 34. They are wanted in connection with an attack at a satirical weekly in the French capital that killed at least 12. [Xinhua photo]

French police were still in a huge manhunt for two of the attackers who escaped by car after shooting dead some of France's top cartoonists as well as two police officers.

Police issued a document to forces across the region saying the men were being sought for murder in relation to the Charlie Hebdo attack.

The document, reviewed by a Reuters correspondent, named them as Said Kouachi, born in 1980, Cherif Kouachi, born in 1982, both from Paris, and Hamyd Mourad, born in 1996.

The police source said one of them had been identified by his identity card, which had been left in the getaway car.

An official at the Paris prosecutor's office said the youngest of the three had turned himself in at a police station in Charleville-Mézières, some 230 kilometers northeast of Paris near the Belgium border.

BFM TV, citing unidentified sources, said the man had decided to go to the police after seeing his name in social media. It said other arrests had taken place in circles linked to the two brothers.

The police source said Cherif Kouachi had previously been tried on terrorism charges and served 18 months in prison.

He was charged with criminal association related to a terrorist enterprise in 2005. He had been part of an Islamist cell that enlisted French nationals from a mosque in eastern Paris to go toIraq to fight Americans in Iraq. He was arrested before leaving for Iraq to join militants.

Police published pictures of the two brothers Thursday morning calling for witnesses and describing the two men as "armed and dangerous."

The police source said anti-terrorism police searching for the suspects and links to them had carried out searches in Reims, Strasbourg and Paris as part of the investigation.

A Reuters reporter in Reims saw anti-terrorism police secure a building before a forensics team entered an apartment there while dozens of residents looked on.

Executions

During the attack, one of the assailants was captured on video outside the building shouting "Allahu Akbar!" (God is Greatest) as shots rang out. Another walked over to a police officer lying wounded on the street and shot him point-blank with an assault rifle before the two calmly climbed into a black car and drove off.

The third man was not seen in any of the footage and it was not clear if he was directly involved in the attack.

A police union official said there were fears of further attacks, and described the scene in the offices as carnage, with a further four wounded fighting for their lives.