U.S. online retail spending on Black Friday surpassed the $1 billion milestone for the first time, researcher comScore Inc. (Nasdaq: SCOR) reported Sunday.

Online retail sales on the day after the Thanksgiving Day holiday rose to $1.04 billion this year from $816 million last year, an increase of 26 percent. As a result, it was the heaviest online spending day to date in 2012, comScore said.

To put this $1.04 billion figure into perspective, researcher ShopperTrak has estimated U.S. brick-and-mortar retail sales were about $11.20 billion on Black Friday.

Reston, Va.-based comScore also reported in its data release that 57.3 million Americans visited online retailers on Black Friday. This represents an increase of 18 percent, year over year.

The top five online retailers with the most traffic on Black Friday were Amazon.com Inc. (Nasdaq: AMZN), Wal-Mart Stores Inc. (NYSE: WMT), Best Buy Co. Inc. (NYSE: BBY), the Target Corp. (NYSE: TGT), and Apple Inc. (Nasdaq: AAPL), comScore said.

Among these top five online retailers, Amazon also led the way in recording the highest growth rate in the number of visitors on Black Friday between last year and this year, comScore said.

“Despite the frenzy of media coverage surrounding the importance of Black Friday in the brick-and-mortar world, we continue to see this shopping day become more and more prominent in the e-commerce channel -- particularly among those who prefer to avoid crowds at the stores," Gian M. Fulgoni, comScore's co-founder and executive chairman, said in a statement.

Fulgoni contended, “With Black Friday online sales up 26 percent and surpassing $1 billion for the first time, coupled with early reports indicating that Black Friday sales in retail stores were down 1.8 percent, we can now confidently call it a multichannel marketing phenomenon."