THE ATTACK IN PARIS: One of the Men Turns himself in, Agency Reports

(CNN)French police say two suspects in Wednesday's terrorist attack on Charlie Hebdo magazine are still on the loose after escaping onto the streets of Paris.

In a statement on their website, French national police ask for information on the whereabouts of suspects Cherif Kouachi and Said Kouachi, warning that both could be armed and dangerous.

Police released photos of the two men, who Paris Deputy Mayor Patrick Klugman told CNN are brothers in their 30s.

Police found an ID document of Said Kouachi at the scene of the shooting, CNN affiliate BFMTV reported. "It was their only mistake," said Dominique Rizet, BFMTV's police and justice consultant, reporting that the discovery helped the investigation.

Citing sources, the Agence France Presse news agency reported that an 18-year-old suspect in the attack had surrendered to police. CNN has not independently confirmed whether the suspect has surrendered.

Police fanned out across France in an intense manhunt for the suspects, who were masked and dressed in black when they burst into the satirical magazine's office Wednesday, killing 12 people.

A tactical unit was deployed in an operation about a 144 kilometers (about 90 miles) from Paris in Reims, France, following the attack, CNN affiliate BFMTV reported. Authorities haven't revealed details about the target of the operation, but speculation surged in French media that investigators could be closing in on the suspects.

French authorities vowed to step up security and apprehend those responsible.

"Everything will be done to arrest (the attackers)," French President Francois Hollande said in a speech Wednesday night. "... We also have to protect all public places. Security forces will be deployed everywhere there can be the beginning" of a threat.

It's too soon to say whether the suspects were operating alone, CNN terrorism analyst Paul Cruickshank said.

Some experts warned that how well the gunmen wielded their weapons, hid their identities and apparently planned their escape showed a marked difference from previous "lone wolf" attacks -- and could be a game changer.