The images were extremely distressing, and Western intelligence services concluded that Syrian government forces did use chemical weapons on its own people, a charge denied by the government.

A group of survivors from the attack in 2013 on the eastern Ghouta region, just south east of the capital, Damascus, are seeking justice in French courts.

Lawyers representing about a dozen survivors have filed a criminal complaint against Syrian officials, whom they blame for the deaths of hundreds of civilians in a rebel held area.

France is home to thousands of Syrian refugees, and it's investigating.

Judges have a mandate to determine whether crimes against humanity were committed anywhere in the world.

The case follows a similar one opened in Germany last year, and it's expected another case will be opened in Sweden in the coming months.

It offers a rare legal avenue for action against the government of President Bashar al Assad.

Attempts by Western powers to set up an international tribunal for Syria have been blocked by Russia and China at the U.

N.

Security Council.

The complaint is based on what the lawyers say is the most comprehensive body of evidence on the use of substances such as sarin gas in Syria.

They include testimonies from survivors and defectors, an analysis of the Syrian military chain of command and hundreds of items of documentary evidence, including photos and videos.