Syria rebels, activists denounce IS attack on Paris

And Syrian activists, refugees, and civilians in the war-torn country expressed their solidarity with France in posts on social media.

Forty-nine armed factions in Syria, including the powerful Jaish al-Islam rebel groups, condemned "in the strongest terms" IS's coordinated assault in Paris that killed at least 129 people.

"We learned today, with great shock and condemnation, about the terrorist attacks against civilians in the city of Paris," the joint statement said.

It called IS's actions "criminal attacks that are against (Islamic) laws and human values".

Most rebel groups in Syria fiercely oppose both the regime of President Bashar al-Assad and IS, which has declared a self-styled "caliphate" in parts of Syria and Iraq.

"This terrorism does not differ from the terrorism that the Syrian people have suffered from every day for the past five years," the groups said.

They pledged to continue to "fight terrorism" and urged the international community to address the root cause of extremism in Syria.

"The real victim of the continuation of the Assad regime and its terrorist organisations is the whole world, not just the Syrian people," the statement said.

Meanwhile, Syrians around the world expressed their solidarity with the people of Paris online.

Activists from the northwest province of Idlib and from the IS-held city of Raqa overlaid their profile pictures on social media accounts with the French flag.

Residents of Douma, a rebel-held town east of Damascus frequently bombarded by Syria's regime, wrote an open letter to the French people.

"First, and before everything, we express our warm condolences to the French families who lost loved ones," the letter said.

"We condemn in the strongest of terms the targeting of civilians there and anywhere around the world," the residents wrote.

"We extend our hands to all the people that love peace and freedom, most of all the French people."