Opposition MEP Andrejs Mamikins of the Harmony party appeared alongside Estonian MEP Yana Toom of the ruling Center Party, who was visiting the dictator for the second time this year, according to Estonian public media source ERR.
As previously reported by LSM, another opposition MEP, Tatjana Zdanoka, visited Assad in July.
According to the official website of the Federal Council, the Russians and three Europeans (Mamikins, Toom and Italian MEP Stefano Maullu) formed a "joint delegation" that met with Bashar al-Assad, parliamentary speaker Hadiey Abbas and even took a tour of a Russian airbase at Hyeymim.
The Russian side included the influential head of the committee on foreign affairs Konstantin Kosachev.
"Members of the delegation congratulated Russian servicemen on the upcoming holidays and wished them the successful performance of combat missions and a speedy return home," the Federal Assembly's website stated.
Photographs on the same website suggest Mamikins was also present at a memorial for Russian troops killed in action in Syria.
Mamikins' visit was condemned by Latvian Foreign Minister Edgars Rinkevics.