German Foreign Minister Sigmar Gabriel has called for an immediate investigation into the alleged gas attack carried out by the Syrian regime on the town of Khan Sheikhoun.

"It is important that the UN and experts from the Organization for the Prohibition of Chemical Weapons (OPCW) gain immediate access and can carry out their investigation without hindrance," Gabriel told the German newspaper "Bild am Sonntag."

At least 80 civilians died in the air attack on the town in rebel-held Idlib province prompting an international outcry. The United States accuses the regime of President Bashar al-Assad of using chlorine gas mixed with a highly toxic sarin-like nerve agent in an air attack.

Gabriel said information Germany has received suggested state forces were behind the attack.

"We have information from our partners and from contacts on that ground that makes it very plausible that the Assad regime was behind this horrible poison gas attack," he said.

In a wide-ranging interview with the German newspaper, Gabriel commented "Assad's future is already behind him."

'Understandable' response

The retaliatory US cruise missile strikes on Friday on a Syrian airbase were "understandable," Gabriel commented.

The missile strikes were the first time the United States has directly targeted al-Assad's forces in the six-year war.  

US officials have said they are trying to assess if Russia played a role in aiding or abetting a chemical attack. Russia and Syria have denied carrying out a chemical attack, instead blaming the incident on chemicals being released after an airstrike hit a "terrorist" arsenal.

Syria agreed to remove its chemical weapons stockpile in 2013 when the US threatened military action after hundreds of people were killed in a sarin chemical attack on a Damascus suburb. 

The Syrian government has been accused of carrying out multiple chlorine gas attacks.  The OPCW in 2016 said that due to gaps and inconsistencies in Syria's declaration its compliance with the chemical weapons treaty could not be fully verified. 

Use of chlorine weapons is prohibited under the international chemical weapons convention, but production of chlorine is not. Syria's use and possession of sarin, if proven, would be a major violation and clear indication it did not abide by the 2013 deal.

cw/jm (AFP, dpa)