French police are searching for two remaining suspects in the attack on Charlie Hebdo in Paris: Cherif Kouachi, aged 32, and his 34-year-old brother Said.
Police have released pictures of the brothers to the media.
There are reports that the youngest of the three suspects identified earlier - Hamid Mourad, aged 18 - has been taken into custody after surrendering to police.
Reuters, quoting a police source, reported police had carried out searches in Reims, Strasbourg and Paris.
Reuters say French police identified one of the alleged attackers after finding his identity card in the getaway car.
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French news broadcaster Itele says the suspect who handed himself in to police earlier has produced an alibi.
NBC's coverage that one suspect had been killed now reported as incorrect.
Paris police say arrest warrants had been issued for Cherif Kouachi, 32 and his 34-year-old brother Said who are "likely armed and dangerous"
Suspects' photos released - French police have released pictures of the brothers wanted over magazine massacre.
CNN says survivors have told of the gunmen asking for people by name before opening fire.
Sources tell AFP that 18-year-old Hamyd Mourad surrendered to police at 23:00 local time on Wednesday "after seeing his name circulating on social media". "He has been arrested and taken into custody," another source told the agency.
Hamyd Mourad, the youngest of the three suspects, has surrendered to police, sources have told AFP.
Police hunt for suspects - French police are hunting three men, including two brothers, suspected of carrying out the attack on satirical weekly Charlie Hebdo that left 12 dead in Paris, a source close to the investigation tells AFP.
Police are searching for two brothers in their thirties, including one who was sent to prison in 2008 for participating in jihadist networks attempting to send fighters to Iraq. The third suspect is aged 18,the source adds.
American television network NBC tweeted this unconfirmed report.
In the report on its website the network quoted a US official who had spoken on condition of anonymity.
The killers were earlier named in the French media as Said and Chérif Kouachi, brothers aged 34 and 32, and Hamid Mourad, aged 18.
The ABC tweeted this image of two of the suspects.
Chérif was reportedly part of an Iraqi jihadist network dismantled in the 19th arrondissement in Paris, near where the attack took place. He was jailed for three years on terror charges in May 2008.
Two addresses in Paris were raided and a search was carried out in Reims, reported to be the home town of one of the men.
French anti-terror police launched the late-night raid in Reims in a frantic manhunt for masked gunmen who shouted "Allahu akbar" as they killed 12 people at the magazine's Paris office, sparking global condemnation.
Local television showed black-clad sharpshooters from the elite police unit in the streets of Reims.
Several thousand police were deployed to find the gunmen,
"They are considered dangerous and heavily armed," the source added.
Either the suspects will be able to escape, or "there will be a showdown", said a member of the unit, urging journalists at the scene to remain "vigilant", AFP reported.
Eight hundred soldiers and five hundred armed police have been deployed in Paris since the alert level was raised to the maximum after the attack on Charlie Hebdo.
Troops are guarding railway stations, armed police are guarding media buildings, and there's ultra-tight security at department stores, which are half-empty on what was supposed to have been the first day of winter sales.
Schools are also on high alert. Trips and outdoor activities have been suspended until further notice by the ministry of education.