Chinese e-commerce giant Alibaba Group Holding Ltd said it racked up more than $5 billion in transactions in the first hour of its annual 'Singles' Day' sales blitz on Friday -- a third more than in the first hour of last year's spree.

The 24-hour event held annually on Nov. 11 offers a benchmark for Alibaba's performance and an insight into China's swing to online shopping, especially via smartphones. Launched in 2009, Alibaba's version of the event was designed to encourage consumers without a partner to treat themselves.

Always accompanied by celebrity razzmatazz - sports stars David Beckham and Kobe Bryant attended Alibaba's countdown this year - Singles' Day shifts more goods than Black Friday and Cyber Monday in the United States combined. Sales on Alibaba platforms, which include Tmall and Taobao, are tipped to exceed $20 billion this year, up from $14 billion last year.

"Back in 2013, 35 billion yuan ($5.15 billion) was our one-day GMV (gross merchandise volume)," said Chief Executive Officer Daniel Zhang in a live microblog posting on Alibaba's event. "Now we can achieve it in one hour."

MOBILE SHOPPING SURGE

Sales officially opened at midnight, releasing a wave of pre-orders that shoppers had placed ahead of the event and propelling the first billion dollars of transactions in just under 5 minutes, Alibaba said on its official microblog.

Alibaba is not the only retailer to mark Nov. 11 with a massive sales drive. China's no. 2 e-commerce player - and bitter Alibaba rival - JD.com Inc and many others also offer discount deals on the day.

The rise of Singles Day reflects how China's consumers, armed with smartphones, are racing online to shop - to the detriment of bricks and mortar stores. Alibaba said on Friday 84 percent of sales in the first two hours were via mobile devices, up from last year.

For Alibaba, extending the expansion of Singles Day could help consolidate sales growth this quarter after a 55 percent surge in second-quarter revenue. The firm co-founded by billionaire entrepreneur Jack Ma beat analyst estimates for July-September on the back of strong core e-commerce sales as well as growth in media and entertainment.

But cut-throat competition for customers on Singles' Day has caused concern over false advertising and massaged statistics. This week China's business regulator warned mainland online shopping platforms against suspect sales tactics.

In May this year, Alibaba said the U.S. Securities and Exchange Commission was looking into how it reports its Single's Day figures. Alibaba said at the time it was cooperating with the authorities, and that the SEC advised it the investigation should not be seen as an indication the company had violated federal securities laws.