Alibaba, the Chinese e-commerce giant, said on Saturday its Singles' Day sales extravaganza hit $25.4 billion, smashing its own record from last year and cementing it as the world's biggest shopping event.

Once a celebration for China's lonely hearts, Singles' Day has become an annual 24-hour buying frenzy that exceeds the combined sales for Black Friday and Cyber Monday in the United States, and acts as a barometer for China's consumers.

As tills shut midnight on Saturday, Alibaba's live sales ticker registered 168.3 billion yuan, up 39 percent from 120.7 billion yuan last year. The dollar figure was up more steeply due to the strength of the yuan against the greenback this year.

The event began soon after a star-studded event in Shanghai late on Friday. As midnight hit, a deluge of pre-orders helped drive a billion dollars of sales on Alibaba's platforms in the first two minutes and $10 billion in just over an hour.

"In terms of scale it just dwarfs any other event out there," said Ben Cavender, Shanghai-based principal at China Market Research Group.

At just past the halfway mark, the headline gross merchandise volume swept past last year's dollar total just shy of $18 billion. Shortly afterward, sales surpassed the 2016 total in the local currency.

The event gets shoppers around China scouting for bargains and loading up their online shopping carts, while delivery men - and robots - brace for an estimated 1.5 billion parcels expected over the next six days.

"This is a big event for China, for the Chinese economy," Joseph Tsai, Alibaba's co-founder and vice chairman, said. "On Singles Day, shopping is a sport, it's entertainment."

Tsai said rising disposable incomes of China's "over 300 million middle-class consumers" was helping drive the company's online sales — and would continue. "This powerful group is propelling the consumption of China," he said.

The final total — more than the GDP of Iceland or Cameroon — leaves other shopping days in the shade. Cyber Monday in the United States saw $3.45 billion in online sales last year.

Investors closely watch the headline number, though some analysts say the way it is calculated is too opaque. The U.S. Securities and Exchange Commission launched a probe into Alibaba's accounting practices in 2016, including into its Singles Day data. That investigation is as yet unresolved.