Judges issue arrest warrant for Syria's president Assad

French judges have reportedly issued international arrest warrants for Syria's President Bashar al-Assad, his brother Maher al-Assad and two other senior officials over the use of banned chemical weapons against civilians.

The warrants, which refer to charges of complicity in crimes against humanity and complicity in war crimes, follow a criminal investigation into chemical attacks in the Syrian town of Douma and district of Eastern Ghouta in 2013.

The attacks killed more than 1000 people.

It is the first international arrest warrant issued for the Syrian head of state, whose forces responded to protests that began in 2011 with a brutal crackdown UN experts have said amounts to war crimes.

These are also the first international arrest warrants issued over the chemical weapons attack in Ghouta, said Mazen Darwish, lawyer and founder of the Syrian Center for Media and Freedom of Expression, which filed the case in France.

Syria denies using chemical weapons but a previous joint inquiry of the United Nations and Organisation for the Prohibition of Chemical Weapons found the Syrian government used the nerve agent sarin in an April 2017 attack and has repeatedly used chlorine as a weapon.

The Syrian presidency and information ministry did not immediately reply for comment.

"The president is responsible for many crimes in Syria but with this type of weapon in particular, sarin gas, it's impossible to jump over the gap," Darwish told Reuters, noting that approval from the president as commander of the armed forces would be mandatory.

Arrest warrants for sitting heads of state are rare because they generally enjoy immunity from prosecution.

However, international law has exceptions when a head of state is accused of war crimes and crimes against humanity or genocide.

The International Criminal Court currently has two arrest warrants against heads of state: one against sitting Russian President Vladimir Putin and another against former Sudanese president Omar al-Bashir.

Assad was shunned for more than a decade by most countries in the region and the rest of the world, with a few rare trips to Russia and Iran since the war broke out in 2011.

His visit to the United Arab Emirates last year signalled a thaw in relations and was followed by a diplomatic flurry following this year's deadly earthquake in Syria.

He has since been welcomed back into the Arab League and travelled as far as China.

Assad's brother Maher was deemed complicit in his role as head of the fourth armoured division.

Judges from the crimes against humanity unit at the Paris Tribunal have issued a total of 11 arrest warrants for crimes committed by Syrian officials.