Online spending remained strong in early December, a period that usually marks a lull in the U.S. holiday shopping frenzy, comScore said on Sunday.
For the week ending December 9, consumers spent $5.9 billion online, up 15 percent from the same period a year earlier, according to comScore, which tracks Internet activity.
E-commerce spending for the first 39 days of the 2011 holiday season reached $24.6 billion, also up 15 percent versus the corresponding days last year, comScore added.
Earlier in the season, the day that has become known as "Cyber Monday" saw a record $1.25 billion spent online in the United States, up 22 percent from last year. Other early season shopping days were also strong, with "Black Friday" e-commerce sales jumping 26 percent from a year ago.
That sparked concern that sales could weaken later in the season, but so far that has not happened, comScore Chairman Gian Fulgoni said on Sunday.
"These highlights represent another very positive sign for the holiday shopping season, as the week following 'Cyber Week' often experiences relative softness in spending momentum due to retailers pulling back on their promotional activity," he said.
The latest data suggests a "strong finish" to the holiday shopping period online this year, Fulgoni added.
This coming week is usually the busiest for online retailers, beginning with "Green Monday," a term coined by eBay in 2007 to describe the Monday occurring around the second week of December, which has tended to be among the heaviest online spending days of the year.
Over the past six holiday shopping seasons, "Green Monday" has ranked among the top spending days of the season, ending the year as the top-ranked twice (in 2005 and 2007) and the second-ranked spending day three times (in 2006, 2008 and 2010), according to comScore data.
"Green Monday will rank among the top online spending days of the season, but it's hold on the No. 1 position may be slipping," Fulgoni said.
That may be because "Free Shipping Day" is becoming more important. This is a day when thousands of merchants offer free shipping on one of the last days that allows enough time for packages to be delivered in time for Christmas Eve, December 24.
Free Shipping Day is December 16 this year and these kinds of promotions may be helping to spread online spending throughout the week. In the past, spending was more concentrated earlier in the week, comScore's Fulgoni noted.
(Reporting by Alistair Barr, editing by Maureen Bavdek)