India and Russia signed defence and energy deals worth billions of dollars after a meeting of their leaders in the southern Indian state of Goa on Saturday.
The 16 agreements announced in the presence of Russian President Vladimir Putin and Indian Prime Minister Narendra Modi included a deal to acquire a Russian missile system and joint production of helicopters and frigates.
Putin and Modi also remotely inaugurated a project to build two new reactors at the Kudankulam nuclear power plant in Tamil Nadu state, which is being developed with Russian technology.
The ceremonies followed delegation-level talks between Putin and Modi on the sidelines of the BRICS summit of five emerging economies, where Russia and this year's host country India are joined by Brazil, China and South Africa.
Alongside defence, an area in which Delhi and Moscow have a partnership going back to over 60 years, the two Cold War allies also announced closer cooperation on sectors ranging from space, hydrocarbons, smart cities and railways.
Key agreements included one under which India would procure Russian S-400 Triumf missile systems that can be used against aerial targets within a 400-kilometre range and joint manufacture of Russian Kamov 226T helicopters and four 11356 frigates for the Indian armed forces.
Four missile systems would cost 5.8 billions dollars and 200 choppers one billion dollars, NDTV news channel estimated. There was no official confirmation of what the deals were worth.
Another announcement was the acquisition of India's second-largest private oil firm Essar Oil by Russia's state-controlled oil giant Rosneft and its partners in a deal valued at 12.9 billion dollars.
A roadmap for celebrations to mark the 70th anniversary of establishment of Russia and India's diplomatic relations in 2017 was also announced.
"An old friend is better than two new friends," Modi said after the meeting, while Putin mentioned the strength of the relationship.
The two countries have been holding the annual BRICS summit since 2000, alternately in India and in Russia.
The latest summit comes against a backdrop of Russia joining military exercises with Pakistan with whom New Delhi has troubled relations, and India's increasing cooperation with the United States.