Syria conflict
US warning comes amid reports of Russia's increased military activity in Syria in support of President Bashar al-Assad Sergei Karpukhin/Reuters

US Secretary of State John Kerry has warned Moscow to back off from Syria, saying its military presence would only escalate violence in the war-torn country. Russia's Foreign Ministry had confirmed on Wednesday morning (9 September) that it has stepped up support for the embattled Assad regime, and admitted its top military experts were on the ground to assist forces loyal to President Bashar al-Assad.

Meanwhile, the Al-Nusra Front, which is fighting against Assad's rule, said it had taken over a military airbase in the northwestern province of Idlib. The group claimed it killed around 100 government forces and captured 60.

Kerry called Russian Foreign Minister Sergei Lavrov and warned him that "such activity could intensify the raging civil war there [in Syria]". John Kirby, a spokesperson for the US State Department, said: "[John Kerry] reiterated our concern about these reports of Russian military activities, or build-up if you will, in Syria and made very clear our view that, if true and borne out, could lead to greater violence and even more instability in Syria."

The US has been monitoring the movement of Russian military personnel in Syria and unnamed officials claimed that two Russian amphibious ships unloaded gear at the Syrian port of Tartus, though the exact nature of the cargo is not known. Further, satellite images showed "more than 100 Russian naval infantry troops on the ground", along with "dozens of vehicles".

Also spotted were "at least three Antonov An-124 planes offloading building supplies and air traffic control equipment in Syria", CNN reported. The US has been equipping rebel forces to oust President Assad, while Russia has been supplying weapons to Syrian forces, in accordance with its bilateral contract. However, both Washington and Moscow are equally opposed to the Islamic State (Isis) insurgence in Iraq and Syria.