Inspectors from the world's chemical arms watchdog arrived Saturday in the Syrian town of Douma, where an alleged chemical attack took place earlier this month, the Russian foreign ministry said.
A team from the Organisation for the Prohibition of Chemical Weapons (OPCW) have been in Syria for a week but had not travelled to the city because of security fears.
"According to the information we have, the special OPCW mission... arrived on the morning of April 21 in the city of Douma at the sites suspected of having toxic substances," the ministry said in a statement.
"The security of the OPCW has been guaranteed not only by the Syrian side but also by the Russian command in Syria."
Dozens were killed in the suspected gas attack in Douma, near Damascus, on April 7, widely blamed on President Bashar al-Assad's forces, according to emergency workers.
The Syrian government has consistently denied using chemical arms and invited the OPCW to investigate.
The Russian ministry said it expects the OPCW to carry out an "impartial investigation".
"Especially since this is the first visit to the scene of a suspected chemical incident in the history of the so-called Syrian chemical record," it said.