NEW DELHI: A group of Indian military personnel is leaving for Russia in the next few days to undergo training on key operational aspects of the S-400 air defence systems as Moscow looks at supplying the first batch of the missile to India later this year, officials said on Tuesday. Russian Ambassador Nikolay R Kudashev interacted with the group at an event in the Russian embassy on Tuesday during which he said the S-400 programme is one of the flagship projects in further boosting military cooperation between the two countries. He said Indo-Russia military and military-technical ties were based on "ever growing extraordinary mutual interest", coherence, consistency and complementarity.