Online shoppers didn't wait around until Cyber Monday to start their holiday shopping.

According to IBM Corp. research unit Coremetrics, U.S. consumers spent 20 percent more online on Black Friday, the day after Thanksgiving, this year than last, while online sales jumped 39 percent on Thanksgiving Day.

Coremetrics measures sales data from more than 500 online retailers, including half of the top 50. It doesn't reveal its partners or specific dollar figures.

Both Coremetrics and e-commerce payment site PayPal, a united of eBay Inc., said shopping by mobile phone is increasingly substantially this year. PayPal said it saw five times more mobile payments worldwide this Thanksgiving, compared with last year.

And Coremetrics said about 17 percent of Black Friday visitors to retail websites came via mobile devices, up from about 5 percent a year ago.