If the President of India is convinced that a grave situation is threatening the security of India due to war, external aggression or armed rebellion, the constitution allows for a national emergency to be called.
The third emergency, that lasted from 1975 to 1977, was declared by PM Indira Gandhi due to internal disturbances. The order bestowed upon the Prime Minister the authority to rule by decree, allowing elections to be suspended and civil liberties to be curbed.
Source: https://en.wikipedia.org/wiki/The_Emergency_(India)#Political_and_civic_unrest
Source: https://en.wikipedia.org/wiki/The_Emergency_(India)#Political_and_civic_unrest