This frame grab from video released on July 22, 2017, and provided by the government-controlled Syrian Central Military Media, shows Hezbollah fighters firing a missile at positions of al-Qaeda-linked militants in an area on the Lebanon-Syria border.
Over the course of Syria's seven- and-a-half year civil war, Israel has publicly admitted to having struck hundreds of Hezbollah convoys and other targets in Syria - more than 200 in the past year and a half alone - while keeping mum on hundreds of other strikes attributed to it. The plane is reportedly a Boeing 747 of the airline Fars Air Qeshem, linked to the Iranian Revolutionary Guard Corps, which had been converted into a cargo plane.
Israel said the munitions warehouse was manufacturing "accurate and lethal weapons", which were "about to be transferred, on behalf of Iran, to Hezbollah in Lebanon", according to a statement from the IDF.
Putin "reminded" Netanyahu that such operations "violated Syrian sovereignty" and said "agreements around the prevention of unsafe incidents were not observed".
Netanyahu on Tuesday expressed his "sorrow" to Putin in a phone call, offering to assist Moscow in the investigation.
But Israel denied the accusations, saying that "when the Syrian Army launched the missiles that hit the Russian plane, (Israeli) jets were already within Israeli airspace".
The Russian Defense Ministry said a missile from Syria's S-200 air defense system shot down the Il-20 surveillance plane with Russian servicemen by mistake because an Israeli airstrike took place at the same time, blaming a simultaneous Israeli strike as the cause of the mistake.
The Russian Defense Ministry is upgrading security on Russian military bases in Syria, and installing automated control instruments, Deputy Prime Minister Yuri Borisov told reporters on Wednesday, following the downing of an Ilyushin-20 plane by the Syrian defense system.
A Lebanese Shiite supporter of the Iranian-backed Hezbollah group, holds a portrait of Hezbollah leader Sheikh Hassan Nasrallah, during activities to mark the ninth of Ashura, a 10-day ritual commemorating the death of Imam Hussein, in a southern suburb of Beirut, Lebanon, Wednesday, Sept. 19, 2018.
In general, regarding Iran's presence in Syria, the USA says Iran has to go.
The Russian military also said the ill-fated plane was used as a cover by the Israeli air force, and that Moscow reserves the right to give a due response.
While offering his honest condolences, Assad blamed the death of the Russian soldiers on the "Israeli smugness and arrogance".
"This is the first Russian casualty in the Israeli-Iranian war of attrition", Center for Naval Analyses analyst Michael Kofman told the National Interest.
On Thursday, Nasrallah claimed Israeli strikes in Syria to prevent Hezbollah from acquiring precise missiles were ineffective.