Hooded gunmen stormed the Paris offices of Charlie Hebdo in the worst militant assault on French soil in recent decades. The dead included top editors at Charlie Hebdo as well as two police officers.
"The lions of Islam have avenged our Prophet," said Abu Mussab, a Syrian who fights with the Islamic State, which has captured broad swathes of Iraqi and Syrian territory.
"These are our lions. It's the first drops -- more will follow," he said, speaking via an internet connection from Syria. He added that he and his fellow fighters were happy about the incident.
"Let these crusaders be scared because they should be."
No group has so far claimed responsibility for the attack.
Abu Mussab said he did not know the gunmen who carried out the attack, but added "they are on the path of the emir .... and our Sheikh Osama (bin Laden)."
His reference to the emir is to Islamic State leader Abu Bakr al-Baghdadi, whose group is a powerful anti-government paramilitary force in both Iraq and Syria and has a growing network of followers elsewhere in the Middle East and Asia.
Al Qaeda founder Osama bin Laden was killed by U.S. special forces in Pakistan in 2011.