For over four decades, India had been raising the issue of terrorism, Modi said in his monthly 'Mann ki Baat' programme.
"Initially the world did not take us seriously, but now the world is realising the destructive aspects of terrorism ... The world will have to join hands to eliminate terrorism," he said.
The Prime Minister said terrorism and extremism made an "unholy attempt" to damage the country's social fabric and it was essential that all humanitarian forces became aware of the problem.
"This is the land of lord Mahavir, Buddha, Guru Nanak and Mahatma Gandhi, which has given the message of peace and nonviolence...Terrorism is hell-bent on destroying humanitarian forces. Therefore, humanitarian forces not only of India but of the entire world will have to unite to defeat terrorism," he said.
Scores of people were killed on this day in 2008 in terror attacks across Mumbai.