Russia backtracked Wednesday over claims that Syrian rebels had used chemical weapons, saying the information still had to be checked.
The foreign ministry said on Tuesday it had information from Damascus the rebels had used chemical weapons in an attack that day in Aleppo province that Syria claimed killed 16 people.
But Deputy Foreign Minister Gennady Gatilov, Russia's pointman on the Middle East, said there was no clear evidence proving the use of weapons of mass destruction.
"The story concerning the use of chemical weapons in Syria must be meticulously investigated," Gatilov wrote on his Twitter account.
"For now, there is no unequivocal evidence about this."
Russia is viewed as one of Syria's closest allies and has three times blocked UN sanctions against President Bashar al-Assad's regime.