A Kremlin spokesman says Russia would consider sending troops to Syria if Damascus were to make such a request.
Quoted by Russian news agencies on September 18, Dmitry Peskov said that, if such a request is made, it will be "discussed and considered," but he insisted the question is purely hypothetical at this stage.
On September 17, Russia urged the United States and its allies to engage the Syrian government as a "partner" in the fight against the Islamic State extremist group amid concerns over an ongoing Russian military buildup there.
Syrian Foreign Minister Walid al-Moallem denied reports on September 17 that Russian combat troops were fighting in Syria but said Syria would not hesitate to ask for Russia's help if needed.
However, a Syrian military source told Reuters the same day that the Syrian military, which has lost ground to rebels recently in a four-year-old civil war, had begun using new types of air and ground weapons supplied by Russia.
Russian Nationals Fighting For IS
In related news, a Russian official says some 2,400 Russian nationals are fighting alongside Islamic State militants.
Russia's First Deputy Director of Federal Security Sergei Smirnov also said that, in total, there are about 3,000 Central Asian nationals fighting within Islamic State extremist groups.
Smirnov said that the problem of migrants fleeing the Middle East to Europe is only likely to increase, potentially posing "great threat" to Russia.
"The assertion that Moscow's support negatively impacts the situation in Syria -- and the flow of refugees in particular -- is not true. This is due to the expansion of Islamic State in the region," he said.
Smirnov said that there are "some countries that try to evade" international cooperation on fighting terrorism.
"There is a cooperation but not at the right level -- especially with the United States," he said.
Smirnov was speaking to reporters in the Uzbek capital Tashkent on September 18 after a meeting on fighting terrorism of senior officials from the Shanghai Cooperation Organization, which brings together Russia, China, Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan.
Based on reporting by Interfax, Reuters, AP, and TASS