Syrian regime Foreign Minister Walid al Moualem on Thursday blamed the suspected chemical gas attack in Idlib on Daesh and the opposition.
Speaking to media, Moualem said, "Al Nusra Front and Daesh and other organisations continue to store chemical weapons in urban and residential areas."
Scores of people died and many were injured after a regime air strike allegedly dropped chemical bombs onto the town of Khan Shaykhun on Tuesday.
Moualem said, ''If it were an air strike using chemical weapons, it would have spread across an area larger than one kilometre in diameter. We did not and will not use chemical weapons, not just against our own people, but even against the terrorists."
But rebels have denied that there were any military positions in the area targeted in Tuesday's air strike.
Initial results of tests on victims point to possible exposure to sarin gas, Turkey's health ministry said on Thursday.
Doctors from the World Health Organisation (WHO) said victims showed symptoms consistent with reactions to a nerve agent.
The UN Commission of Inquiry on Syria and the Organisation for the Prohibition of Chemical Weapons (OPCW) both said they were investigating the attack.
Britain, France and the US have drafted a UN resolution that would demand Syria provide information on its flight operations as part of an OPCW probe.
Conditions set for any international inquiry
Moualem said the regime has also set conditions for any international inquiry into the suspected chemical attack, saying it must not be "politicised."
He said the regime's Russian allies have put forward ideas for the formation of a "non-politicised commission of inquiry."
Syria's past experience with international inquiries had not been encouraging, he added.
He said the regime would only decide on the idea once its concerns were addressed.
Meanwhile, the UN has called the US, Russia, Turkey and Iran to help establish a 72-hour ceasefire in Syria in order to deliver humanitarian aid to remote areas and also to the 400,000 people trapped in eastern Ghouta near Damascus.