| A Russian defence ministry video showed a Tupolev Tu-22M3 dropping bombs over Syria |
Russia's defence ministry says it has used a base in western Iran to carry out air strikes in Syria.
| Dozens of people have been killed in air strikes on rebel-held areas of Aleppo in recent weeks |
Iran is Bashar al-Assad's main regional ally and has provided significant military and financial support since an uprising against him erupted in 2011.
The US State Department said Russia's use of an Iranian base was "unfortunate but not surprising". Asked about moves towards a possible agreement with Russia to co-operate in fighting so-called Islamic State (IS), a spokesman, Mark Toner, said closer Russian-Iranian ties would not necessarily preclude a deal. But he added: "We're not there yet."