Gunmen gesture as they return to their car after the attack outside the offices of French satirical weekly newspaper Charlie Hebdo (seen at rear) in this still image taken from amateur video shot in Paris January 7, 2015. REUTERS/Reuters TV

WASHINGTON (Reuters) - A U.S. drone strike in Syria has killed an Islamic State militant linked to the Jan. 7 2015 attack on satirical weekly Charlie Hebdo in Paris, defense officials said on Friday.

Boubaker el Hakim was killed late last month in Raqqa, the Islamic State’s defacto capital in Syria, the officials said, adding he was believed to be involved with planning the attack.

Charlie Hebdo, known for its satirical covers gleefully ridiculing political and religious leaders, lost many of its top editorial staff when brothers Cherif and Said Kouachi, armed with assault rifles and other weapons, broke into an editorial meeting and killed 12 people and wounded 11 others.

The attacks prompted a worldwide solidarity movement, with the “Je Suis Charlie” (I am Charlie) slogan going viral on social media.

Islamic State, which has controlled parts of Iraq and Syria in recent years, has lost some territory this year to Iraqis and Syrians supported by a U.S.-led coalition of air strikes and advisers. Apart from the killings at Charlie Hebdo, Islamic State sympathizers around the world have carried out other shootings and bombings of civilians.