An Azeri presidential aide said on Saturday that Russia has been supplying Armenia with weapons since a clash between the two former Soviet republics in July.
More than a dozen Armenian and Azeri soldiers were killed in July at the border between the two, which have long been at odds over Azerbaijan's breakaway, mainly ethnic Armenian region of Nagorno-Karabakh.
Russia has called the conflict is a highly sensitive matter.
Hikmet Hajiyev, a senior adviser to Azerbaijan's President Ilham Aliyev, said Russia has been "intensively arming Armenia" right after the July conflict, with Russian Il-76 strategic airlifters flying towards Armenia after July 17.
The Russian foreign ministry did not immediately reply to a Reuters request for comment.
Russia has a military base in Armenia and considers it to be a strategic partner in the South Caucasus region and supplies it with weapons.
Russia told Azerbaijan that those Il-76 planes were carrying building materials, Hajiyev said, adding that Baku was not satisfied with this answer.
"Construction materials are usually not supplied in aeroplanes, there are other tools for that," Hajiyev said.
"Based on observations we also have information that arms are being shipped to the Syrian territory via the Armenia territory," he added.