Iranian President Hassan Rouhani has congratulated Syria's Bashar al-Assad on a victory in "liberating Aleppo", Assad regime officials said on Wednesday.
Rouhani said this was an important step towards "wiping out terrorism in Syria", the regime's Twitter account and state media reported.
Iran is a key military ally of Damascus.
Assad regime forces and Iran-backed Shiite militias attacked Aleppo on Wednesday, violating the latest truce reached after mediation efforts from Turkey, while the sound of explosions were heard in the city on early in the day.
Assad regime forces and Iranian-backed militias have been carrying out executions in Aleppo, entering homes and killing some civilians "on the spot". The United Nations said that some 85 civilians were killed by regime forces on Tuesday, however, the number given by local sources is much higher.