The e-commerce giant said that amount was more than a third of the USD 5.8 billion full-day sales recorded on the same day last year and analysts say this year will blow that out of the water.
Alibaba has been pushing November 11 as Singles Day -- so named for the number of ones in the date -- since 2009 as it looks to tap an expanding army of Internet shoppers in China, which has the world's biggest online population.
The day was originally marketed as an "anti-Valentine's Day" in China featuring hefty discounts to lure the country's singletons and price-sensitive buyers.
It has been expanded globally this year to include overseas merchants and customers.
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Within the first hour and 12 seconds, more than USD 2 billion) of deals were settled on both domestic and international retail marketplaces, Alibaba said in a statement, adding that 45.7 percent of the transactions were made via mobile devices.
The giant operates China's most popular online shopping platform, Taobao, which is estimated to hold more than 90 percent of the online market for consumer-to-consumer transactions.
The company does not sell products directly but acts as an electronic middleman. It also owns other marketplaces, including business-to-consumer platform Tmall.
More than 27,000 brands and merchants are participating in this year's Singles Day, while consumers in more than 220 countries and regions will be able to join the 24-hour spending spree, the statement said.