The deals were announced following talks held between Prime Minister Narendra Modi and Russian President Vladimir Putin on the sidelines of the BRICS summit being held in Goa.
The development comes as Russia hopes to stave off tough competition from the Americans and the Europeans to continue being India's foremost defence supplier.
The most strategically important decision is the inter-governmental agreement for the purchase of S-400 'Triumf' long-range air defence missile system which has the capability to destroy incoming hostile aircraft, missiles and even drones at ranges of up to 400 km.
India and Russia have been in talks for over a year for the purchase of at least five systems of S-400 that will be a game changer in the region.
It is capable of firing three types of missiles, creating a layered defence, and simultaneously engaging 36 targets. If India signs the deal, it would be the second customer of the prized missile system after China which had struck a $3 billion contract last year.
Another important deal is for four Admiral Grigorovich-class (Project 11356) guided-missile stealth frigates.
Under this deal, two vessels will come from Russia while the other two will be built in India with Russian collaboration.
No decision has been made on the selection of the Indian shipyard.
This is in furtherance to the six Talwar-class frigates that Russia built for the Indian Navy between 2003 and 2013.
The complex agreement for production of 200 Kamov 226T helicopters domestically under a nearly $1 billion deal to replace the country's aging Cheetah and Chetak choppers is yet another important defence deal between the countries.
Here's everything about the S-400:
- The S-400 Triumf, previously known as S-300PMU-3, is an anti-aircraft weapon system.
- It is developed by Russia's Almaz Central Design Bureau in the 1990s.
- The S-400 is an upgrade of the S-300 family and has been in service with the Russian Armed Forces since 2007.
- The S-400 uses three different missiles-extremely long range 40N6, long range 48N6 and medium range 9M96 missile-to cover its entire performance envelope.
- Just one system comprising up to 8 divisions (battalions) can control up to 72 launchers. It can also handle a maximum of 384 missiles.
- A successful test firing of the missile was conducted at an airborne target at a range of 400 km (250 mi), in April 2015.
- To increases the probability of complete destruction of targets, all the missiles are equipped with directed explosion warhead.