Images from the Syrian town of Khan Sheikhoun on Thursday showed men collecting evidence from the site of the chemical attack that killed at least 70 people including children.
This as Damascus again denied it was behind the attack, despite being blamed by Western countries including the US.
The Syrian foreign minister called a media conference in the face of mounting international pressure and commented on Russia’s idea of an inquiry.
Walid Moallem said: “There are a number of questions relating to the formation of such a commission.
“We need to ensure that it is not politicised, that it is neutral, with broad representation, and that it should start its work from Damascus, not from Turkey.”