India has signed a $5 billion deal with Russia to buy S-400 air-defense systems.
The deal, signed October 5 on the sidelines of a meeting between Russian President Vladimir Putin and Indian Prime Minister Narendra Modi in India's capital, New Delhi, was praised by the two leaders in a joint statement.
The deal is almost certain to provoke tensions with the United States, which imposed sanctions against China last month over purchases of Russian weaponry, including S-400-related equipment.
Putin said at a press conference after the talks that an agreement was also signed to develop six nuclear power projects in India.
Putin said that he and Modi also agreed on bilateral cooperation in India's plans to launch a manned space mission.
U.S.-Russia ties have plunged to the lowest level since the end of the Cold War over Russia's annexation of Ukraine's Crimea and Moscow's support to separatists in Ukraine's east.
Earlier this week, Western powers accused Moscow of masterminding a series of global cyberattacks.
India and Russia have been close allies for decades and Moscow remains New Delhi's biggest weaponry supplier.