Two shells struck the Russian embassy compound in the Syrian capital Damascus, BBC reported.
A BBC Arabic correspondent in Damascus says some people have been injured.
The explosions triggered widespread panic and smoke was seen coming from the embassy compound.
Rebel forces based in the suburbs of Damascus have targeted the embassy in the past.
Activist group the Syrian Observatory for Human Rights said the shells had come from an eastern area of the capital.
Before the missiles landed, demonstrators had been waving Russian flags and holding up photographs of Russian President Vladimir Putin, witnesses said.
Russia began its campaign of air strikes in Syria late last month.
The Kremlin says it is attacking ISIS and other jihadists, but the US says other rebel groups opposed to Bashar al-Assad – an ally of Russia – have been targeted.