Moscow: Russian President Vladimir Putin said on Thursday that groundless accusations over a Syrian chemical attack were unacceptable, while Western countries engaged in efforts to saddle Damascus with a new United Nations Security Council resolution.

Putin made the remarks during a phone conversation with Israeli Prime Minister Benjamin Netanyahu, according to a Kremlin statement.

At least 70 people, among them 27 innocent children, were killed with over 500 others wounded on Tuesday in a toxic gas attack by Syrian warplanes on the Islamic State-held town of Khan Sheikhoun in the country`s Idlib province.

But the Russian Defence Ministry said on Wednesday that the deadly gas contamination was caused by the explosion of chemical weapons produced and stored by the rebels, after Syrian aircraft bombed the area.

Damascus has repeatedly denied possession of any chemical weapons.

During Thursday`s conversation, Putin called the gas contamination "an incident", saying "it is unacceptable to make groundless accusations against any party until a thorough and objective international investigation has been conducted".

US President Donald Trump on Wednesday accused the Syrian government of going "beyond a red line" by attacking civilians with toxic gas.

Western countries are trying to pass a UN Security Council resolution drafted by the US, Britain and France condemning Damascus for its alleged chemical attack.

Russian Deputy Envoy to the UN Vladimir Safronkov said Russia supports on-spot probe into the alleged chemical attack, rather than in a remote way.

Russian Deputy Foreign Minister Gennady Gatilov said Russia was ready to veto the resolution if Western countries rush the vote.

US ambassador to the UN Nikki Haley threatened that her country may take unilateral action if the UN Security Council failed to respond.