One of two brothers suspected of carrying out the deadly shooting at a French satirical weekly visited Yemen in 2011 to train with al-Qaida-affiliated militants, US and European sources close to the investigation said on Thursday.
The sources said Said Kouachi, 34, was in Yemen for a number of months training with al-Qaida in the Arabian Peninsula (AQAP), one of the group's most active affiliates.
He and his brother Cherif, 32, are the subject of a manhunt in France following the killing of 12 people by Islamist gunmen at the offices of the satirical weekly newspaper Charlie Hebdo in Paris on Wednesday.
The two suspects are French-born sons of Algerian-born parents. Both men had been under police surveillance. Cherif was jailed for 18 months for trying to travel to Iraq a decade ago to fight as part of an Islamist cell.
A Yemeni official familiar with the matter said the government was aware of the possibility of a connection between Said Kouachi and AQAP, and was looking into possible links.