US retail sales increased 2.3% on Thanksgiving Day and Black Friday, as against the same period last year, with shoppers spending an estimated total of $12.3bn across the two days that marks the start of the 2013 holiday season, according to a report by research firm ShopperTrak.

ShopperTrak also reported that shopper traffic at brick-and-mortar stores during the two-day period increased 2.8% from last year, to more than 1.07 billion store visits.

According to the report, shoppers visited more stores and spent more money on these two days amid the allure of deep discounts, promotions and extended store hours.

US retailers normally generate 40% of their annual income during the all-important holiday season.

On a regional basis, traffic for the two days increased 2.3% from the prior-year period in the Midwest, while it rose 4.8% in the South and 6.9% in the West. Meanwhile, traffic declined 5% in the Northeast.

Sales in the Midwest rose 3.3% during the two-day period, while it increased 4.8% in the South and 6% in the West. In the Northeast, sales decreased 7%.

ShopperTrak founder Bill Martin said the Black Friday shopping experience is changing with more shoppers choosing to go out on Thanksgiving Day.

"Consumers increasingly research products online before entering stores. When they arrive, customers know exactly what they want to buy – retailers now need to make their experience a satisfying one," Martin added.

However, ShopperTrak noted that data taken separately for Black Friday showed that brick-and-mortar shopper traffic declined 1.4% from the same period last year, while retail sales decreased by 13.2%.