Russia's ambassador to Lebanon told Hezbollah’s al-Manar TV that his country will down any US missiles fired at Syria.
Russia's ambassador to Lebanon has said any US missiles fired at Syria would be shot down and the launch sites targeted.
Alexander Zasypkin, in the comments broadcast on Tuesday evening, said he was referring to a statement by Russian President Vladimir Putin and the Russian chief of staff.
"If there is a strike by the Americans then ... the missiles will be downed and even the sources from which the missiles were fired," he told Hezbollah’s al-Manar TV.
It comes as Russia used its veto power at the United Nations Security Council on Wednesday to prevent an investigation into the attack by Bashar al-Assad's regime on Douma, a besieged town in eastern Ghouta, that killed up to 80 people and injured hundreds more.
Australia has warned the Russian ambassador not to allow Syria to be shielded from investigations into its use of chemical weapons.
Foreign Minister Julie Bishop said Russian ambassador Grigory Logvinov was given the stark warning on Tuesday, after threats his country would use its veto power.
"We urge Russia not to stand in the way into an investigation into the use of chemical weapons in Syria," she said.
"We have advised the Russian ambassador in Canberra yesterday that we expect Russia to fulfil its responsibilities as a permanent member of the United Nations Security Council to not shield the Syrian regime from an investigation into the use of chemical weapons which has killed a number of civilians."
US President Donald Trump has threatened that "everybody's gonna pay a price" for the attack.
Ms Bishop said Australia would support action by the US that was "targeted, calibrated and proportionate".
The US carried out air strikes last year after the Syrian regime used a sarin nerve agent in an attack at Khan Sheikhoun that killed 90 people.
Russia also vetoed an investigation into that attack.
Earlier Labor's foreign affairs spokeswoman Penny Wong said if Russia had no involvement in the attack it should welcome an investigation.
"If Russia and other parties, including the (Syrian) regime believe that they were not involved in this attack then they have nothing to fear from the independent investigation the United Nations is seeking," she told ABC radio.
Additional reporting: AAP