Narendra Modi took the oath of office as India's new prime minister at the sprawling presidential palace yesterday, a moment made more historic by the presence of the leader of arch-rival Pakistan.
Modi's inauguration is the first to which India invited leaders from across South Asia. Heads of governments from Pakistan, Sri Lanka, Mauritius, Maldives, Nepal and Afghanistan attended, and Bangladesh was represented by the speaker of its parliament.
But most eyes remained on Pakistani Prime Minister Nawaz Sharif, whose visit could signal a thaw in ties between the often hostile neighbours.
Indian President Pranab Mukherjee administered the oath to Modi. Outgoing prime minister Dr Manmohan Singh was seated next to Sharif.
Sharif called his visit "a chance to reach out to each other" and "a great opportunity", in an interview. "Both governments have a strong mandate. This could help in turning a new page in our relations," he added.
Modi and Sharif are to hold formal talks today.
US President Barack Obama and Chinese Premier Li Keqiang also sent congratulations to the new Indian prime minister.
Modi unveiled a sharply reduced government of 46 members including himself, a cut of 25 from that of his predecessor Singh, to speed up decision-making and slash bureaucracy.
Minutes after Modi was sworn in, he posted a message on his official website saying that along with the people of India and the world his government would work to "script a glorious future for India".
Watch: Narendra Modi sworn in as India's Prime Minister
"Let us together dream of a strong, developed and inclusive India that actively engages with the global community to strengthen the cause of world peace and development," the statement said. Many supporters see him as India's answer to the neo-liberal former US president Ronald Reagan or British leader Margaret Thatcher.
One foreign editor has ventured Modi could be so transformative he turns out to be "India's Deng Xiaoping ", the leader who set China on its path of spectacular economic growth.
Some 4,000 guests, ranging from members of the defeated Nehru-Gandhi family to top industrialists, Bollywood actors and Hindu holy men, attended the ceremony.
Associated Press, Reuters, Agence France-Presse