Black Friday sales rose just 0.5 percent to $10.66 billion after rising 3 percent in 2008, ShopperTrak said on Saturday, a rise that may disappoint investors who had expected retailers to see a bigger boost this year.

ShopperTrak, which measures customer traffic, said shopper traffic was heavy throughout the country on Friday, the kickoff of the holiday shopping season after U.S. Thanksgiving Day.

Last year, Black Friday sales climbed 3 percent to $10.606 billion. That was much slower than the 8.3 percent rise ShopperTrak saw in 2007, before the brunt of the economic downturn set in for consumers.

This year, many retailers offered deals online and in stores before Black Friday, including on Thanksgiving itself.

Online shoppers spent 35 percent more on Black Friday web purchases than a year earlier, with the average order value reaching $170.19, according to online retail analytics company Coremetrics.

ShopperTrak still believes the 1.6 percent increase it originally predicted for the holiday season remains intact, Co-founder Bill Martin said in a statement on the company's web site.

(Reporting by Jessica Wohl; Editing by Peter Cooney)