A key French member of the Islamic State (ISIS) group, Salim Benghalem, who had ties to the Charlie Hebdo attackers, was sentenced in absentia by a Paris court on Thursday to 15 years in prison, AFP reported.

Six other men, who have returned from Syria and Iraq, were given sentences of between six and nine years.

Benghalem, 35, is thought to have been in Syria since 2013 and is subject to an international arrest warrant.

He is believed to be one of the ISIS jailers of Western journalists and aid workers who were later executed, working alongside Mehdi Nemmouche, who later carried out a fatal attack on the Jewish Museum in Brussels in 2014.

Benghalem is listed as a “foreign terrorist combatant” by the United States, and is known to French intelligence services for his “active participation in combat” in Syria, a security source told AFP last year.

He came to the attention of French authorities for his involvement in the Buttes-Chaumont network of would-be jihadists in Paris that included Said and Cherif Kouachi, who carried out the attack on Charlie Hebdo newspaper exactly one year ago.

Benghalem was jailed in 2007 for his part in gang violence, and was released in 2010, after which he is thought to have travelled to Yemen, a security source said.

He is considered to be a central figure in the recruitment of radicalized young men for ISIS.

Intelligence sources believe Benghalem is one of the highest-ranked foreign fighters in the Islamic State chain of command.

He appeared in an ISIS video released in February, praising the attacks on Charlie Hebdo and calling for more violence.

The daily Le Monde reported that he was the target of a French air strike on the ISIS stronghold of Raqa in Syria in October.

AFP contributed to this report.