In a television address to the nation, Modi said an Indian missile had shot down an Indian satellite in space, making India only the fourth country after the United States, Russia and China to have that capability.
Opposition leader Mamata Banerjee said she was lodging a complaint against Modi with the Election Commission for violating the electoral code of conduct.
"Today's announcement is yet another limitless drama and publicity-mongering by Modi desperately trying to reap political benefits at the time of election (in April-May)," Banerjee, the chief minister of West Bengal state and a potential prime ministerial candidate, said on Twitter.
Randeep Singh Surjewala, a spokesman for the main opposition Congress party, called Modi's announcement a "gross violation of code of conduct."
The Election Commission said in a statement later that the matter had been brought to its notice. "The Commission has directed a Committee of Officers to examine the matter immediately in the light of Model Code of Conduct," it said, without elaborating.
India's general election begins on April 11.
This story has been published from a wire agency feed without modifications to the text. Only the headline has been changed.