Armed French gendarmes swoop on villages in manhunt for newspaper attackers

Demonstrators hold pencils and signs that read "Rio is Charlie" (R) and "I am Charlie" (L) in tribute to the victims of a shooting by gunmen at the offices of French satirical weekly Charlie Hebdo, during a demonstration organized by the NGO Rio de Paz (Rio of Peace) in Niteroi, near Rio de Janeiro, January 8, 2015. [Photo/Agencies]

US government sources said Said Kouachi and his brother Cherif Kouachi were listed in two US security databases, a highly classified database containing information on 1.2 million possible counter-terrorism suspects, called TIDE, and the much smaller "no fly" list maintained by the Terrorist Screening Center, an interagency unit.

US television network ABC reported that the brothers had been listed in the databases for "years."

Dave Joly, a spokesman for the Terrorist Screening Center, said he could neither confirm nor deny if the Kouachis were listed in counter-terrorism databases.

On Thursday, US President Barack Obama made an unannounced visit to the French Embassy in Washington to pay his respects.

In Paris, a policewoman was killed in a shootout with a gunman wearing a bulletproof vest on Thursday morning, setting a tense nation further on edge. Police sources were unable to say whether that incident was linked to the previous day's assault at the Charlie Hebdo weekly newspaper, but the authorities opened another terrorism investigation.

Bewildered and tearful French people held a national day of mourning. The bells of Notre Dame pealed for those killed in the attack on Charlie Hebdo, a left-leaning slayer of sacred cows whose cartoonists have been national figures since the Parisian counter-cultural heyday of the 1960s and 1970s.

The newspaper had been firebombed in the past for printing cartoons that poked fun at militant Islam and some that mocked the Prophet Muhammad himself. Two of those killed were police posted to protect the paper.