Russia's state-owned nuclear company, Rosatom, has announced it will build 16 nuclear reactors in India.
The announcement came during a visit to Delhi by the Russian prime minister, Vladimir Putin, who said nuclear co-operation was one of the most important aspects in the partnership between the two countries, which have strong trade ties.
Rosatom said earlier that six of the reactors would be built by 2017.
Russia is already building two reactors in the southern Indian state of Tamil Nadu.
Russia is competing with French and US firms for contracts to build nuclear power plants in Asia's third-largest economy, which is looking to increase its energy supply in order to sustain rapid economic growth, the BBC reports.
Competition ramped up after India's landmark civilian nuclear deal with the US in 2005 which ended the isolation India had experienced since it tested an atom bomb in 1974.
Coal still accounts for more than 50% of India's energy use - but over the next decade alone, the contribution of nuclear energy is expected to rise from 3% to 6% of the country's total needs.
As part of the deals signed during Mr Putin's visit, Russia will also refit an aircraft carrier, supply an additional 29 fighter aircraft to India and jointly develop transport aircraft.
