NEW YORK (Reuters) - China's online shopping king Alibaba said about US$2 billion worth of goods were sold on the e-commerce giant's websites within the first hour and 12 seconds of Singles Day on Tuesday, its annual 24-hour shopping grabfest.

Alibaba did US$3.1 billion in business in half a day during Singles Day last year, equivalent to what it sold in the full day in 2012.

Half of the US$2 billion gross merchandise volume this year was sold within the first 18 minutes after the "11.11 Shopping Festival" opened, the company said.

Singles' Day - so named because the date Nov. 11 has four singles (11.11) - was started as an in-joke between university students, but has morphed into China's equivalent of Cyber Monday.

Spurred by Alibaba and its network of online retailers, sales have ballooned from US$7 million in 2009 to over US$5.7 billion last year for Jack Ma's company.

This year's festival is global, reaching shoppers in more than 200 countries, the company said.