India and Russia are actively negotiating regarding the sale of S-400 surface-to-air missile systems and the possibility of Russia leasing a second nuclear submarine, Alexander M Kadakin, Russian ambassador to India, told The Pioneer.

Previously, there were reports suggesting the possibility of India inking a deal to purchase S-400 missile systems and taking on lease a second nuclear submarine during the Moscow visit by Indian Prime Minister Narendra Modi in Dec 2015. But no such deals were inked then.

But now Kadakin has revealed about India possibly getting strategically important air defence systems, the S-400, which could be used to protect various Indian cities from enemy missile attacks. The S-400 air defence systems have been deployed in the Moscow region and at Hmeimim air base in Syria, where Russians have been operating from.

The Indo-Russian relationship is Independent of the relationship with other countries, Kadakin said, and added: "We do not feel jealous when India acquires military hardware from other countries for its strategic needs ... " "Please name a country that can lease a nuclear submarine."

Lately, India has been looking to US, Israel and France for military hardware, moving away from its traditional partner Russia for various reasons, some of those being mid-stage cost escalations and delays in the delivery.

But Russia still remains the go-to partner when it comes to certain strategic areas of military co-operation involving key weapons hardware technology. PM Modi had called the Indo-Russian relationship as a "truly strategic" one.

India already had INS Chakra, Akula-class nuclear-powered attack submarine on a 10-year lease from Russia. INS Chakra was commissioned into the Indian Navy in 2012. This will be the second nuclear submarine from Russia.

"The hull of the submarine is ready but it has to be refurbished as per Indian needs after the talks are concluded," Kadakin said.

The indigenously developed nuclear-powered submarine INS Arihant, built with Russian technical support, is currently undergoing sea trials.

Kadakin further revealed that his country will open four service centres in India for the Su-30 MKI jets. He said that an announcement in this regard will be made soon.

India is also looking at buying more MiG 29K fighter jets for INS Vikramaditya, he said. India has already ordered 45 MiG-29K/KUB aircraft.

The Russian envoy said that the deal for India producing 200 Kamov Ka-226 helicopters has been concluded. This will lead to India producing these light utility helicopters with Russian help under the present government's "Make in India" initiative.