Indian billionaire Mukesh Ambani Monday (29 Oct) became the world's richest person, overtaking Microsoft boss Bill Gates, Mexican tycoon Carlos Slim Helu and investment guru Warren Buffett, on the back of a bull run in the stock market.

After a strong share price rally in his three group companies - India's most valued firm Reliance Industries, Reliance Petroleum and Reliance Industrial Infrastructure - the net worth of Mr Ambani rose to US$63.2 billion, the Press Trust of India news agency reported.

In comparison, the net worth of both Gates and Slim is estimated to be slightly lower at around US$62.29 billion each, with the Mexican telecommunications magnate leading the American software czar by a narrow margin.

Buffett, earlier the third richest in the world, also dropped one position like Slim and Gates. He has a net worth of about US$56 billion.

Last month, Forbes magazine had named Gates as the richest American with a net worth of US$59 billion, calculated as of 30 Aug.

The magazine had said that a movement of US$2 in the share price of Microsoft, the world's biggest software maker, could 'add or subtract US$1 billion' from his wealth.

Since end-August, Microsoft's stock price has risen by US$6.58, which results in a gain of US$3.29 billion in Gates' wealth based on Forbes' assumption, the news agency reported. (The Straits Times/ ANN)