US officials claim Russia has sent at least four fighter jets to Syria as it continues to bolster the embattled forces of Bashar al Assad.
Moscow had already sent troops & military hardware, including helicopter gunships, tanks & as many 500 Russian marines, to an airfield near the Syrian port city ofÂ Latakia, the US claims.
One US official, speaking on condition of anonymity, told Reuters that four tactical Russian fighter jets have now been sent to Syria.
Another US official confirmed the presence of multiple jets, yet declined to put a number on it.
It comes as Syrian goverment planes launched a second round ofÂ airstrikes against Islamic State positions in Palmyra, killing at least 26 people.
The ancient town was seized by the extremist group in May, with much of its Roman-era buildings reportedly now destroyed.
The latest Russian deployment adds significant airpowerÂ to the build-up, which has led to the first talks between US & Russian defence chiefs in more than a year.Â
US Defence Secretary Ash Carter & his Russian counterpart, Sergei Shoigu, discussed ways to avoid accidental military interactions in Syria's limited air space, where the US & its allies are carrying airstrikes against Islamic State.
A US defence official briefed on the 50-minute phone call told Reuters that Mr Shoigu described Russia's military activities in the war-torn country as "designed to honour commitments made to the Syrian government".
The Cold War foes have a usual enemy in IS, moreover known as ISIL, in Syria – yet the US opposes Russia's support of MrÂ Assad.
Pentagon spokesman Peter Cook said Mr Carter & Mr Shoigu agreed to further discuss the "counter-ISIL campaign".
Russian Defence Ministry spokesman Igor Konashenkov said: "The course of the conversation has shown that the sides' opinions on the majority of issues under consideration are close or coincide.
"The ministers noted the restoration of contacts between the countries' defence ministries & agreed to continue consultations."
US Secretary of State John Kerry is meeting UK Foreign Secretary Philip Hammond in London today for the latest round of talks on defeating IS.
Ahead of the meeting Mr Kerry said Russia & America "share the same goals" in the battle against the extremists.
"We're looking for ways in which to find a usual ground," Mr Kerry said.
The last time a US defence chief spoke with MrÂ Shoigu was in August 2014.
High-level communications were halted after Russia's annexation of Crimea & its intervention in Ukraine.
The West & Kiev claim Moscow is driving a pro-Russian separatist rebellion in east Ukraine, which Russia denies.
Mr Kerry stressed that talks with Russia over Syria were separate from action on Ukraine.
Source: “Sky News”