World's richest man Jeff Bezos added US$6.28 billion ($9.1b) to his fortune after his company, Amazon, recorded its biggest shopping day in customer history.

The online retail giant announced Cyber Monday had surpassed its previous record, set on the same day last year.

Amazon didn't disclose exact sales figures for the day, but it said customers ordered 180 million items during the five days from Thanksgiving to Cyber Monday.

However, computer software company Adobe has estimated Amazon's Cyber Monday sales hit US$7.9b.

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And Fortune reported Bezos' net worth jumped 5 per cent from the beginning to the end of its record-breaking sales day, while the company's shares shot up by 5.3 per cent.

Black Friday 2018 also surpassed that of the previous year with online sales exceeding US$6b, according to Fortune.

Bezos' net worth currently sits at US$138.5b, up from around US$100b at the start of the year.

It's been a big year for Amazon and its founder and chief executive.

In July, Bezos became the world's richest man in modern history after his net worth broke US$150b.

On September 4, Amazon became the second publically traded company to surpass the US$1 trillion mark, following Apple who achieved the feat a month earlier.