"It was only after learning about such a huge interest from Indians in Sydney that the Indian Prime Minister's Office realised how much significance the Sydney visit could hold for the Indian diaspora," the spokesman said.
In Sydney, the organisers also have plans to highlight a new historical, archaeological and linguistic evidence indicating human migration from the Indian subcontinent to Australia around 5,000 years ago.
"It will show how the link between India and Australia has been much older and deeper than many people believe," he added.
Event organisers in Sydney said more than 21,000 people have registered through their local community organisations to attend the event, which can accommodate only 16,000.
Another 20,000 people are expected to register Monday onwards when organisers open a number of seats for allocation by lottery.Victorian Multicultural Minister Matthew Guy flagged off the train at Southern Cross station - the major railway station and transport hub for Melbourne - amid huge fanfare of Modi who is the first Indian premier to visit the country in the last 28 years.