Cyber Monday sales up 26% from last year by Monday afternoon

NEW YORK (CNNMoney) -- Cyber Monday is off to a strong start, with shoppers flocking to their computers and smartphones to grab online deals.

By Monday afternoon, online sales rose nearly 26% from Cyber Monday last year, according to IBM Digital Analytics Benchmark, which tracks more than one million e-commerce transactions per day from more than 500 retailers.

"Cyber Monday is the Super Bowl day of online shopping ... all signs point to that being the case again today," said Jay Henderson, strategy director at IBM Smarter Commerce.

The 26% increase eclipses both the 21% jump in online sales seen on Black Friday and the 17% increase on Thanksgiving day, IBM found. It's also in line with estimates from data tracking firm ComScore, which put sales at $1.5 billion for Cyber Monday -- a 20% rise from the same day last year.

Many retailers rolled out earlier online discounts this year, contributing to the strong start to holiday sales.

A growing number of people are also using their mobile devices to make purchases. Nearly a quarter of all online traffic this holiday season has come from consumers using smartphones and tablets, according to IBM. On Cyber Monday, about 21% of shoppers used their mobile devices to look at deals online, and 11% made purchases on their phones or tablets -- up from 12% and 7% last year.

Cyber Monday traditionally refers to the Monday following Black Friday and is typically the day many retailers offer online-only deals. This year many companies didn't wait for Monday and instead began rolling out their online discounts on Thanksgiving or earlier.

The retailers that popped up as most-frequently searched by users on Cyber Monday include Walmart, Best Buy, Amazon, Sears and Target. The products that were searched the most online were Amazon's Kindle and Kindle Fire, Uggs, iPads, the iPod Touch, Legos and the Wii, according to Experian Marketing Services.

This year, online sales have outpaced in-store sales. Retail sales at stores on Black Friday declined nearly 2%, according to ShopperTrak, while online sales posted double-digit growth.