The Indian Navy has reportedly signed INR50bn ($679.26m) contract with Russia to extend the service life of its Kilo-class submarines.
As part of this development, the navy has finalised a contract with Russian shipbuilder Zvezdochka to upgrade the underwater vessels to keep them in service for a period of 35 years, The Economic Times reported.
Under this project, the refit of one submarine will be performed in Russia, while the remaining will undergo renovation in India.
The upgrade of the first submarine, INS Sindhukesari, is expected to start in June next year. The vessel will be equipped with Klub land attack cruise missile.
Navy officials were quoted by the Economic Times as saying: "The idea of a second mid-life refit of Indian submarines has been discussed between Russia and India since 2010.
"The process of upgradation will take a little over two years."
The Russian Kilo-class submarines (Type 877EKM) have been designed to support anti-submarine (ASW) and anti-surface ship (ASuW) warfare missions.
Powered by diesel-electric propulsion with two diesel generators and one propulsion motor, Type 877EKM submarine features MGK-400 sonar, active radar with a target separation system, as well as a radar warning receiver and a direction finder.
With a surfaced displacement capability of 2,300t, the submarines have a maximum diving depth of 300m and can cruise at a surfaced speed of 10k with a range of 6,000nm.
Russia has built ten Kilo-class submarines for the Indian Navy.
The Indian Navy has awarded the contract for the first submarine, while the decision on the remaining will be taken after reviewing the capability of Indian yards to perform the upgrade.