Russian President Vladimir Putin on Thursday slammed “unfounded accusations” over the “incident with chemical weapons” in Syria in a phone call with Israeli Prime Minister Benjamin Netanyahu, the Kremlin said.

“There was an exchange of opinions over the incident with chemical weapons that took place in the Syrian province of Idlib on April 4,” the Kremlin said in a statement.

“Putin in particular underlined the unacceptability of making unfounded accusations against anyone before a thorough and impartial international investigation is carried out,” it said.

Israel has joined a chorus of Western allegations that the forces of Bashar al-Assad were behind a suspected chemical attack on rebel-held Khan Sheikhun that left scores dead.

Moscow has sought to deflect blame from its ally Assad over the incident and says Syrian jets struck a rebel arms depot where “toxic substances” were being put inside bombs.