NEW DELHI (Reuters) - Prime Minister Narendra Modi on Thursday appealed to millions of people of Indian origin across the world to turn to their homeland after he eased visa rules to lure overseas talent, in a bid to make the country a top power.

India has the world's second largest diaspora after China, with more than 25 million people settling overseas since colonial times, from Guyana in South America to Singapore in East Asia.

Modi's desire to harness the group's skills and resources is bolstered by his Hindu nationalist leanings towards reasserting India's position as a global leader with a unique civilisation stretching back thousands of years.

"There was a time when professionals in India went to distant lands to explore new possibilities," Modi told an annual gathering for people of Indian origin in the western state of Gujarat. "Now India awaits you with opportunities."

The diaspora event was timed immediately prior to a large investment meeting that will be addressed by US Secretary of State John Kerry and World Bank President Jim Yong Kim.

On Wednesday, President Pranab Mukherjee approved an executive order to ease the way for those whose families left India as many as four generations ago, as well as their spouses, to get lifetime visas and own property in India.

Modi's pitch has a harder economic aspect too, as the diaspora holds investments of more than US$100 billion (S$125 billion) in India.

Young, foreign-educated Indians came back in droves at the turn of the millennium and poured in funds as the economy took off with a roar, but the flow has dried up as growth sputtered in the past few years. Modi is keen to reverse that trend.

Officials said they are also assisting citizenship efforts by those whose ancestors left India centuries ago, shipped by British rulers to distant corners of the globe as indentured labourers.

Last year, overseas Indians greeted Modi with a rockstar welcome and stadium rallies on his state visits to the United States and Australia.

The energetic leader's popularity has already won over some high-profile individuals, including Arvind Panagariya and Arvind Subramanian, two of the world's top economists, who recently joined his government after long careers in the United States.

The diaspora meeting was attended by Guyana's President Donald Ramotar, and also sought to tap into the French-speaking Indian diaspora from island nations such as Mauritius.