World powers engaged in a series of blame trading and increasingly volatile rhetoric on Thursday in the aftermath of a suspected gas attack in the Syrian town of Khan Sheikhoun.

One day after Russia vetoed a United Nations resolution put forward by the UK, US and France to blame Damascus for the attack, Moscow backed a claim by the government of Syrian President Bashar al-Assad that the catastrophe was the result of an airstrike against a rebel warehouse that happened to be storing chemical weapons.

The Kremlin issued a statement saying that Russian President Vladimir Putin found it "unacceptable to make groundless accusations against anyone without conducting a detailed and unbiased investigation."

In response, Turkey's President Recep Tayyip Erdogan said it had "saddened us that this has not been understood," by Moscow, and that the Kremlin continued to ask "is Assad behind this or not?" even after it had become clear that Damascus was to blame.

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According to activists, at least 86 people were killed due to the release of a chemical nerve agent, and hundreds more needed medical attention for respiratory problems and other severe injuries. The attack occurred in Idlib province, an area on the Turkish border mostly controlled by al-Qaeda affiliated rebels.

Turkey suspects sarin use

Despite initial confusion over the exact nature of the substance, the Turkish Health Ministry said on Thursday that it had conducted autopsies on several victims and could confirm that they had been subjected to chemical weapons, most likely the internationally outlawed sarin gas.
Read: Syria's chemical weapons, explained

The French government immediately called for Assad regime to be prosecuted over the incident.

"These crimes must not remain unpunished…one day, international justice will rule on Assad," said French Foreign Minister Jean-Marc Ayrault in an interview with CNews television. German Chancellor Angela Merkel added that it was a "scandal" that the UN resolution had failed.

Syria: International inquiry only under our conditions

Damascus has said it is open to the idea of an international investigation, but only on very strict terms. Top diplomat Walid al-Moualem said Syria had been subjected to biased inquiries by the global community in the past, and would not allow that to happen again.

"It must not be politicised, it must leave from Damascus and not Turkey. We have numerous questions about this subject. When we are certain these questions are addressed with convincing answers, we will give you our response," he said.

Moualem also reiterated the claim, echoed by Moscow, that the tragedy occurred because the rebels had been stockpiling sarin gas, and the Syrian army had no way of knowing it was there.

"I confirm to you once again that the Syrian Arab Army has not and will not use this type of weapon against our people and our children, and not even against the terrorists who kill our people," the foreign minister said.

US looks at military intervention

After marking a monumental shift in six years of US policy calling for Assad to step down, in recent weeks top US officials such as Secretary of State Rex Tillerson and UN envoy Nikki Haley have said it was no longer a major priority.

Events in Khan Sheikhoun.appeared to have changed matters, however. Tillerson said on Thursday that "there is no doubt in our minds, and the information we have supports that Syria, the Syria regime under the leadership of President Bashar al-Assad are responsible for this attack."

He cautioned Moscow to "consider carefully their continued support for the Assad regime."

President Donald Trump said that Assad had commited an "affront to humanity" and that "the message from the United States must be that this will not stand." 

An official from the Defense Department told reporters that the Pentagon was preparing plans for a range of possible military options the United States might take in response to the attack.

es,dm/rt (AFP, AP, Reuters)