Dec. 3 (Bloomberg) -- Online spending at U.S. retailers jumped 15 percent on Dec. 1 to $846 million, the second-biggest amount on record, as Internet sites lured customers with discounts on clothing and electronics, ComScore Inc. said.

The so-called Cyber Monday was the first workday after the Thanksgiving holiday weekend. The Reston, Virginia-based research firm reiterated today its forecast for Internet holiday spending to be little changed from a year ago.

“Consumers are clearly responding positively to retailers’ aggressive online discounts,” ComScore Chairman Gian Fulgoni said in a statement. “We can but hope that their aggressive discounting has still left room for profits.”

Internet site visits increased 10 percent on Dec. 1, Nielsen Online said in a separate statement yesterday.

EBay Inc., Amazon.com Inc. and Wal-Mart Stores Inc. had the most visitors overall, the New York-based research firm said. Among the top 10 most visited retail sites, Sears Holding Corp. and Best Buy Co. had the biggest gains as they lured customers with discounts.

The one-day best for online spending is $881 million, set last December, ComScore said.

Amazon.com climbed $3.45, or 8.4 percent, to $44.64 at 10:15 a.m. in Nasdaq Stock Market composite trading.

To contact the reporter on this story: Brad Skillman in New York at bskillman1@bloomberg.net.

Last Updated: December 3, 2008 10:18 EST