Russia's foreign ministry has complained of a "strange hysteria" over Moscow's actions in Syria, as western countries expressed concerns over apparent preparations for military intervention.
Foreign ministry spokeswoman Maria Zakharova said that “Russia has never made a secret of its military-technical cooperation with Syria” and confirmed that “Russian military specialists are in Syria to help them master the weapons being supplied”.
She said there was nothing out of the ordinary about their presence.
However, there have been signs of more intensive Russian activity in Syria, including reported sightings of Russian jets and combat vehicles, claims of increased weapons deliveries, and even reports that prefab housing was being erected to pave the way for a major military presence.
Photographs have been posted on social media networks from Tartus naval base by men who appear to be Russian contract soldiers.
The base, which Russia has maintained since the 1970s, was previously a small and low-significance maintenance outpost, but is seeing increased activity.
Russia has insisted there is nothing out of the ordinary about the military assistance.
Syrian government officials have also played down recent reports about an enhanced Russian military role, but insists that Moscow remains a supportive ally.
Always there
“Russian experts are always present, but in the last year they have been present to a greater degree,” a Syrian official told reporters.
“All aspects of the relationship are currently being developed, including the military one.”
President Bashar al-Assad did not comment on the question when it was raised by Russian journalists, who interviewed him on Sunday.
On the diplomatic front, however, western officials say they detect signs of greater readiness by Moscow to push for a negotiated solution to the Syrian crisis, in part because of its growing concerns about the threat from Islamic State.
Some analysts speculate that the Russian president, Vladimir Putin, may try to use the current concern over Islamic State and the refugee crisis to call for an international coalition against terrorism involving Russia.
“If additional measures in the interests of boosting anti- terrorism efforts are required on our part, this issue will be considered accordingly, but exclusively on the basis of international law and Russian legislature,” Ms Zakharova said.
Meanwhile, Syrian state TV has reported that insurgents led by Jabhat al-Nusra, al-Qaida’s Syrian affiliate, had captured the Abu Zuhour airbase after a two-year siege.
This leaves almost the entire northern province of Idlib empty of government forces.
Sandstorm capture
The UK-based Syrian Observatory for Human Rights said insurgents had captured the base under the cover of a severe sandstorm that has raged across the country.
Insurgents now control nearly the entire province, except for the predominantly Shia villages of Foua and Kfarya, which are in the hands of pro-government militia.
Meanwhile, fighting is continuing for Zabadani, northwest of Damascus, a strategic position for Assad’s Lebanese ally Hezbollah.
Talks on a ceasefire there have included a proposal that the town’s defenders, who are from the Sunni Islamist group Ahrar al-Sham, be exchanged for the Shias of the two Idlib villages.
This proposal is seen by some observers as introducing an explicitly sectarian element into the Syrian conflict.