Online spending at U.S. retailers on Monday jumped 15 percent over with the comparable day a year ago to $846 million, comScore said Thursday, as consumers sought out bargains in a tough economy.

The Monday after Thanksgiving was nicknamed "Cyber Monday" by the National Retail Federation to describe the surge in online spending when customers return to work after Thanksgiving and shop from their desks.

Online shopping is popular among consumers who want to compare prices for the best deal, so usage can increase in a tough economy when shoppers are paying more attention to costs.

ComScore (nasdaq: SCOR - news - people ) said a 22 percent rise in the number of buyers drove the increase, even though the average amount shoppers spent declined 5 percent. ComScore attributed the drop in dollars per buyer to each buyer completing fewer transactions.

ComScore representative Gian Fulgoni said nearly two million more consumers bought items online this year because of "extremely attractive" prices offered by retailers.

"But because of their reduced spending power, it's also evident that those who did buy were unable or unwilling to spend as much per person as we saw last year," Fulgoni said in a statement.

The most visited retail site was eBay Inc. (nasdaq: EBAY - news - people ), which recorded nearly 13 million visitors, up 45 percent from last year, followed by Amazon.com Inc. (nasdaq: AMZN - news - people ) with 9.2 million visitors.