French intelligence services have pledged to release proof within days that Syrian government forces carried out a chemical weapons attack in the north west of the country earlier this month.

The gas attack in Khan Sheikhoun killed more than 80 people, including up to 30 children on April 4th.

The attack, which has been widely blamed on the Syrian President Bashar al Assad's regime, prompted US President Donald Trump to order a cruise missile strike on one of the country’s airbases.

A question of days

In a television appearance, French Foreign Minister Jean Marc Ayrault said an investigation into the gas attack is currently underway by French intelligence services and military intelligence.

“It is a question of days and we will provide proof that the regime carried out these strikes," Mr Ayrault told LCP television.

"We have elements that will enable us to show that the regime knowingly used chemical weapons," he added. "In a few days, I will be able to provide proof."

The Assad regime has consistently denied it was behind the attack – and both Russia and Iran have condemned the US cruise missile strike response.

Syrian denial

Syrian government personnel have claimed the attack was either a rebel provocation or the result of Syrian planes hitting a rebel weapons factory.

Mr Assad last week questioned whether the attack happened at all, saying there are "a lot of fake videos now."

"We don't know whether those dead children were killed in Khan Sheikhoun," he said in an interview with AFP TV. "Were they dead at all?

"Who committed the attack, if there was an attack? What's the material? You have no information at all, nothing at all. No one investigated."

Russia and Iran have issued a joint call for a new "full-scale and thorough investigation" into the attack.

Moscow last week vetoed a UN Security Council resolution demanding a swift investigation into the attack – the eighth time Russia has used its veto to protect the Assad regime since bloody civil war erupted in Syria in 2011.

"Incontrovertible" evidence

Separately the Organisation for the Prohibition of Chemical Weapons (OPCW) has said "incontrovertible" test results by its team of experts already probing the incident had shown sarin gas or a similar substance was used in Khan Sheikhoun.

The governing body of the global chemical arms watchdog is now expected to vote on a fresh investigation.

However, Moscow has criticised the OPCW for not sending experts to the attack site, saying it was "unacceptable to analyse events from a distance."

In response, OPCW director general Ahmet Uzumcu said a team was ready to head to the town "should the security situation so permit."

"I am told that this would require a 48-hour ceasefire and safe passage for the team to be arranged," he said.

A UK analysis of samples from the scene of the attack – also dismissed by Moscow – detected a sarin or sarin-like substance.

Additional reporting from IRN ...