NEW YORK (CNN/Money) - Shoppers flocked to the Internet for their holiday gift shopping over the Thanksgiving weekend, ringing up $1.2 billion in total online sales, a market research group said Wednesday.

ComScore Networks, an e-commerce market research firm based in Reston, Va., said total sales for the week ended Nov. 30 rose 25 percent over the same period a year ago.

Consumer electronics, software, home and garden products, and music saw the strongest sales, all with 40 percent to 70 percent growth over last year, the report said.

"With the full month of November in, the holiday season to date is up approximately 30 percent to $5.26 billion," the report said. Internet sales for the same period last year rose 19 percent to $4.1 billion.

ComScore expects total online retail spending for the key holiday period of November and December to be up about 25 percent to 30 percent to between $12.1 billion and $12.6 billion. Holiday sales in 2002 rose 19 percent to $9.7 billion.

Gian Fulgoni, chairman of comScore Networks, attributes the strong growth of online retail sales to a confluence of factors.

"People are increasingly using the Internet for easy price comparisons. Many retailers have streamlined their web sites and made them easier to navigate," Fulgoni said. Also, the reliability of delivery of a product bought over the Internet has increased."

But despite a strong start to the holiday shopping season, Fulgoni said he remains cautious. "We'll see if holiday spending will remain strong throughout the season. Last year the season also started strong but didn't stay that way."