With a net worth of $76 billion, Bill Gates reclaimed the top spot after a four-year hiatus, toppling Mexico's telecommunications mogul Carlos Slim Helu, who placed second at $72 billion, Forbes said in announcing the list on Monday.

With a networth of $18.6 billion, Reliance Industries Ltd (RIL) chief Mukesh Ambani leads the pack of 56 billionaires based in India featured on the list.

His younger brother Anil Ambani is ranked 281st on the list with a net worth of $5 billion.

However, Forbes said the richest Indian person has seen "precipitous decline" in his fortune since 2008 when his networth was $43 billion and he when was the world's fifth richest person.

"Regardless he remains India's richest person and is still bullish; says he plans to invest $25 billion in his businesses over the next 2 years," Forbes said.

The magazine also referred to accusations of wrongdoing made against Reliance by Aam Admi Party founder Arvind Kejriwal, who had recently alleged that Ambani is "running the government".

The other Indian billionaires in the list are ArcelorMittal chairman and CEO Lakshmi Mittal who is ranked 52nd with a networth of $16.7 billion, Wipro chairman Azim Premji ranked 61st with $15.3 billion, founder of Sun Pharma Dilip Shanghvi ranked 82nd with $12.8 billion, HCL co-founder Shiv Nadar is ranked 102nd and has a net worth of $11.1 billion. Hinduja brothers came in at the 122nd with $10 billion.

Birla group chief Kumar Birla is ranked 191st and has a networth of $7 billion, Forbes said the ranks of the world's billionaires continued to scale new heights and stretched to new corners of the world.

The list has 1,645 billionaires with an aggregate net worth of $6.4 trillion, up from $5.4 trillion a year ago.

Amancio Ortega, the Spanish founder of clothing conglomerate Inditex SA, which includes the Zara fashion chain, ranked third at $64 billion.

Investing icon Warren Buffett, who runs Berkshire Hathaway and is a frequent bridge partner for Gates, was fourth at $58.2 billion. Oracle Corp chief Larry Ellison came in fifth at $48 billion.

The list features a record 268 new ten-figure fortunes, including 42 new women billionaires.

In total, there are 172 women on the list, more than ever before and up from 138 last year.

Wal-Mart Stores heiress Christy Walton was the highest-ranking woman, in ninth place, at $36.7 billion. France's Liliane Bettencourt, who got much of her wealth from cosmetics company L'Oreal SA, was next among women at $34.5 billion, and ranked 11th overall.

The internet was well-represented. Google founders Larry Page and Sergey Brin ranked 17th and 19th, worth a respective $32.3 billion and $31.8 billion, while Amazon.com's Jeff Bezos was between them at $32 billion.

Facebook founder Mark Zuckerberg, 29, more than doubled his net worth to $28.5 billion, and ranked 21st.

Former New York City Mayor Michael Bloomberg, who left office two months ago, was 16th at $33 billion, built mainly through his eponymous media company.

Forbes said the year's biggest loser was Brazilian tycoon Eike Batista, whose net worth fell below $300 million from $10.6 billion as his oil and natural resources empire collapsed amid too much debt and falling output.

Roughly two-thirds of the world's billionaires, or 1,080, were self-made. The United States had the most billionaires, with 492, followed by China at 152 and Russia at 111. Algeria, Lithuania, Tanzania and Uganda joined the list with one each.