Operations of the Israeli air force are undertaken in violation of Syria's sovereignty, Russian President Vladimir Putin told Israeli Prime Minister Benjamin Netanyahu by phone on Tuesday.Putin made the remarks after the Russian Defence Ministry said earlier in the day its Il-20 surveillance plane with 15 servicemen on board was mistakenly downed by a Syrian missile on Monday night due to a simultaneous Israeli air strike that confused Syria's air defence system, Xinhua news agency reported.In this case, the Russian-Israeli agreements on the prevention of dangerous incidents in Syria were not observed, Putin said at the phone conversation, according to a Kremlin press release.Putin urged the Israeli side to prevent such situations from now on.According to the Kremlin, Netanyahu expressed condolences over the deaths of the Russian troops on board the Il-20.To conduct a thorough investigation of the tragedy, Netanyahu promised to provide detailed information on the actions of the Israeli aircraft over the Syrian territory on Monday.Earlier in the day at a press conference, Putin said the downing of the Russian Il-20 plane was the result of "a chain of tragic and random circumstances" and Russia will beef up security measures for its soldiers in Syria.