NEW YORK (MarketWatch) -- Strong discounts brought U.S. consumers to the stores on "Black Friday" -- the traditional first day of the holiday shopping season -- with estimated sales rising 3% from last year, according to industry analyst ShopperTrak RCT Corp.

ShopperTrak said in a report Saturday that preliminary sales for Black Friday totaled $10.6 billion. This year's rise in sales, while lower than the 8% increase seen for the day last year, comes despite plummeting consumer sentiment data and other economic turmoil.

"Retailers should be cautiously optimistic as deep discounts drove consumers en masse to various retail locations to spend, despite myriad economic pressures seen over the last two months," ShopperTrak said.

Black Friday refers to the day after Thanksgiving, so called because many retailers begin to turn a profit on that day, moving from "red ink" to "black ink." Sales for the day are seen as a key harbinger for the overall holiday season.

Regionally, the South led the gains with a 3.4% rise over 2007, closely followed by the Midwest, up 3.0%; the West, up 2.7%; and the Northeast, gaining 2.6%.

ShopperTrak cited retailers' early openings and "numerous door buster specials" and other promotions.

"While this is an encouraging start for retailers, there's no guarantee these deep discounts will continue after Black Friday weekend, which could slow spending," said Bill Martin, co-founder of privately-held ShopperTrak.

"Additionally, consumers have just 27 days to shop this year as opposed to 32 in 2007, which may catch some procrastinating consumers off guard, leading to lower sales levels," he said.

The ShopperTrak National Retail Sales Estimate covers retailers of general merchandise, apparel, furniture, sporting goods, electronics, hobby, books and other related store sales.

Consumer survey also cheerful

Separately, a survey of shoppers for the National Retail Federation said Sunday that average spending over the Black Friday weekend -- both at physical stores and over the Internet -- rose 7.2% from last year.

From Thursday through Saturday and including projected spending for Sunday, shoppers spent an average of $372.57, compared to last year's $347.55, it said.

The retail group's 2008 Black Friday Weekend survey, conducted by BIGresearch, also said more than 172 million shoppers visited stores and Web sites over the weekend, up from 147 million shoppers in 2007.

The survey polled 3,370 consumers and has a margin of error of plus or minus 1.7%.

The NRF said it continues to project that holiday sales will rise 2.2% this year to $470.4 billion.