NEW YORK (CNNMoney) -- Preliminary reports for Black Friday indicate that retailers may have seen their strongest sales ever during the all-important kick-off to the holiday shopping season.

Retail sales on Black Friday climbed 6.6% this year to an estimated $11.4 billion, according to ShopperTrak, which tracks foot traffic at malls and stores. Last year, sales climbed just 0.3% to $10.7 billion, which was a record one-day sales amount at the time, according to the company.









"This is the largest year-over-year gain in ShopperTrak's National Retail Sales Estimate for Black Friday since the 8.3 percent increase we saw between 2007 and 2006," said ShopperTrak founder Bill Martin. "Still, it's just one day. It remains to be seen whether consumers will sustain this behavior through the holiday shopping season."

However, sales have been strong throughout the entire month of November with retailers rolling out holiday deals earlier than ever. In the two weeks leading up to the week of Black Friday, retail sales were up 3.6% and 3.8%, respectively, ShopperTrak reported.

"Retailers continue to stretch out Black Friday weekend by enticing shoppers with doorbuster deals weeks in advance," said Martin.

Online sales have also proven to be strong, with many big-box retailers and department stores offering deals online earlier this year.

Online sales were up 39.3% on Thanksgiving Day and 24.3% on Black Friday compared to the same days last year, according to IBM's (IBM, Fortune 500) Coremetrics, which tracks real-time data from 500 retailers in the apparel, department store, health and beauty and home goods categories.

"This year marked Thanksgiving's emergence as the first big spending day of the 2011 holiday season with a record number of consumers shifting their focus from turkey to tablets and the search for the best deals," said John Squire, chief strategy officer at IBM's Smarter Commerce division.

Consumers also spent slightly more than they did last year, although they spent most of that money on themselves. According to NPD Group consumers spent about 3% more on purchases during Black Friday. However, about 44% were self purchases up from 33% last year, the research group said.