UN Special Envoy for Syria Staffan de Mistura arrived on Sunday in Tehran and held a meeting with Iranian Deputy Foreign Minister for Arab-African Affairs Hossein Jaberi Ansari, a diplomatic source told Sputnik.On Thursday, de Mistura announced he would visit Tehran in the coming days to inform the Iranian authorities about the latest developments in Syria and the ceasefire violations in the Arab republic's most populous governorate of Aleppo.