Russia has sent an advanced missile system to the Syrian port of Tartus, as tensions escalate between Moscow and Washington over the five-year conflict.
The announcement came after Washington said it was suspending talks with Moscow aimed at reviving a ceasefire deal.
President Assad’s forces advanced on rebels during intense street fighting in the opposition-held east of Aleppo city, which Russia has been accused of bombing indiscriminately including targeting its hospitals.
The UN rights chief called for action to halt the “ghastly avalanche of violence” unfolding in Syria’s second city, which is reeling from some of the most brutal fighting in the conflict.
Russia, which has denied its strikes have hit hospitals, said it was deploying an s-300 missile system to Tartus on the Mediterranean coast.
Pentagon spokesman peter cook said the Russian missile system would not affect operations in the US-led air campaign in northern Syria.